It has finally occurred to me that we might be dealing with different types of personal philosophies that go beyond D&D in general. If true, that would mean coming to a total understanding of different perspectives would be beyond the scope of a D&D discussion. So, I'll test that hypothesis.
OK, I finally decided to break down and respond to the specific questions. However, I think that it bears pointing out that social expectations regarding hosts and guests break down pretty quickly when relating them to DM/Player relations, in my opinion. Social convention has a wide variety of factors involved that aren't necessarily contained within the game (for example, many social gatherings have an implied obligation of attendance where it would be rude of the guest to not attend, regardless of desire).
Additionally, I feel it bears stating that the host/guest relationship is, IMO, very much a mutual social contract. A host is equally responsible for making their guests feel comfortable and welcome as the guest is responsible for respecting the host's expectations and wishes. As such, violating that contract on either part (not minor transgressions, but flat out violating it) absolves the other party of their obligations. (This conversation is quickly reminding me of Thidwick the Big-Hearted Moose.)
1. You are invited to a party. Your host and some of his/her friends don't <fill in the blank (smoke, drink, eat gluten, listen to rap, whatever)> and request that people not bring such things to the party.
Would you consider the that the host is being a jerk or out of line by not allowing certain things at his party?
No, I typically wouldn't consider the host to be a jerk in these situations. One aspect off this is that these are reductive requests, not additive requests. Both can be reasonable, but there are different expectations involved. Reductive requests such as these are typically made to ensure that each person at the party is comfortable, welcome, and safe. As a guest, I would ASSUME that the host had good reasons for such a request, and I would respect them, no matter how bizarre I felt they were.
To comment on a few specifics, I, too, am of the camp of "Who brings there own music to a party?" That just strikes me as odd, as music is part of atmosphere, and atmosphere is the responsibility of the host. That being said, I don't think it would be rude or unusual for a guest to suggest listening to something different.
I also find it interesting that so many people seemed to draw the line at gluten free. I know several people that have gluten allergies or celiac disease, so this isn't some bizarre lifestyle choice; it has serious health consequences if they eat gluten. I think it is quite reasonable to attempt to have multiple options for such people, or to at least request that people clearly mark what is and isn't gluten-free (or peanut free, mushroom free, etc.). Again, this is to ensure that all of their guests feel welcome and included, rather than relegating some poor sap to only being able to eat one bland dish in the corner.
Anyway, circling back around, reductive requests like this usually are made because the inclusion of such a thing negatively impacts a guest or guests, and the lack thereof typically won't really negatively impact the other guests (I personally don't know of anybody who gets severely ill by NOT eating gluten, NOT drinking alcohol, or NOT smoking around others).
2. You are invited to a themed-party (costume, birthday, Super Bowl, Star Trek, etc). The host asks you to bring your <fill in blank with appropriate implements of recreation>.
If it were a Star Trek party on Super Bowl Sunday, would you ask people to turn off Star Trek so you could watch the Super Bowl?
If it were a Super Bowl party, would you start DJing your "best of Star Trek" collection in the background? Would you feel the host was being a jerk if he asked you to stop?
These tend to be more along the lines of additive requests instead of reductive requests. In general, I think a host making these requests is quite reasonable. However, I would most likely think the host rude to refuse somebody entry for not complying (e.g., "Hey, you're not wearing a costume! Sorry, can't come in."). An additive request should be encouraged of a guest, and possibly even rewarded (e.g., a prize for the best costume), but negative reinforcement is not polite on a hosts part, and a non-compliant guest shouldn't be refused or ostracized.
As to sticking with the theme, this is a more nuanced answer, to me. A host requiring participation would be rude in my estimation; though, again, encouragement, persuasion, and reward is totally acceptable. I think it is personally reasonable for a guest or group of guests at a Superbowl party to go into a separate room and talk about or watch Star Trek. However, it WOULD be rude of the guests to insist that the game be turned off. Not participating and forcing others to not participate are two entirely separate actions. If the stated theme or goal of the party is to do one particular activity, that activity should not be removed as an option.
As a further aspect, however, I think a host needs to be flexible. The purpose of hosting a party is to provide enjoyment for the guests. if nobody is having fun doing the planned activity, the host should probably read the room and try and find a way to get everyone having fun, rather than religiously sticking to an activity.
3. You and a bunch of friends meet up "to hang out and have some fun." One of you is driving. The driver insist on going where he wants to go, and tells anyone who doesn't want to do it that he'll drop them off at their home, but it's his car and he's driving it to where he want to go.
Would you consider him to be being a jerk?
Yes, I would probably consider him to be a bit of a jerk in this situation. This is not a host/guest situation to me. The host/guest aspect of this would apply to the rules inside the car. The driver, in my opinion, gets to pick the music on the radio (or at least have veto power) and can set rules such as no eating in the car. Heck, I could even see it as acceptable that the driver require some gas money. However, in the situation defined, it sounds like it's setup to be a group consensus of destination with the purpose being the group spending time together. It would be rude to have the implication be, "We should all hang out and find something fun to do", and then dictate only one option after the fact. On the flip side, if the driver said, "I"m going to the movies, would anyone like to come?", then the driver is under no obligation to drive anyone anywhere except the movies. It's all about the expectations given at the outset.
Anyway, social situations have a lot of their own rules that are nuanced and don't necessarily directly apply to an RPG group. Additionally, there are numerous cultural conditions that apply to social situations that make even finding hard and fast rules difficult to ascertain.
As an example, I spent a semester of college in London. As an American, there were numerous situations that required quite an adjustment. One cultural expectation that was very hard for me to adapt to initially was the concept of buying rounds at the pub. In America (or at least my experience in it, it's a big country), it is generally accepted that each person is responsible for their own drinks. If somebody offers too buy a round, it is usually considered a magnanimous and generous offer, but is never expected. In England (again, my experience of it), it was common practice that each person would take turns buying a round for the table. If you refused to do so and only paid for your own drinks, it was considered rude and a bit antisocial. At first, I felt really uncomfortable with this, but then I adapted to it, and it truly did seem to encourage the social camaraderie of the situation. These are two entirely different approaches to the same activity, and are equally valid within their social constructs.
Additional food for thought: often times one person is DMing a game that is being hosted in the house of one of the players. This can bring all sorts of interesting conundrums in the DM/Player responsibilities compared to the host/guest responsibilities.