So, where do the chips really fall on this issue? Is it really an issue or are some bad DMs and some bad players making both sides of this seem more prevalent than really needs to be addresed through the 5E ruleset?
In the OP's rant, it looked to be an example of bad DMing. The "Because I said so," fails on so many levels. Granted, it's good to have Rule 0, but it's not so great when it's used heavy-handed and arbitrarily or even worse-yet, in the middle of the game. Nothing is more frustrating than creating a character using the PH only to find in mid-game the DM says, "Oh, you picked that. Well, I don't like it. You don't get to use it."
However, on the other side of the coin there are bad players who try to use "logic" or realism in order to bend or break the rules. The example was another post in which the DM argued with the player about not being able to act because a guy charged him from a distance of 60 feet. The charging character won initiative, could charge, and attack. The player character was flat-footed, did not have initiative. Those were the rules, end of story. It may not seem "logical" or realistic, but it's the rule set in which to frame combat and play by.
There are ways to mitigate this behavior and this is what I do for my group:
1. I write up a campaign primer. It has the creation guidelines and what books are considered "legal" for play. If there is anything that I have banned, it's listed here. I rarely like to ban anything though unless it goes against the theme of the campaign.
2. I list all my houserules out and how they work. Everything else in the legal books applies. I only like to create thematic houserules for the specific campaign, but I will have only 1 or 2 actual houserules that will go from campaign to campaign. My personal rule of thumb is that I don't like creating a bunch of houserules.
3. If something turns out to be broken like a powerful feat/spell combo move, we'll discuss it after the session, but I will not, ever, ban or change it mid-stream in the game. If something annoys me, I let the player have his fun for the session and then we talk about it. If the player insists on keeping it, I usually acquiesce but with the warning that monsters / NPCs are likely to have it too if it's particularly effective.
Now for gamers who believe there should be DM empowerment / player entitlement, I would say there should be reasonable
expectations in play. A player should be able to read the PH and play by the rules written. The DM should be able to establish before the campaign starts or after a session any house rules, modifications, or changes--hopefully to fit the theme of the campaign or to deal with problematic rules, but have a good reason to, and not to do so based on pettiness or whim.