The question with the klingons is always: how to keep them from taking our stuff without resorting to their tactics. Those are the dramatic situations I like to see characters work through.
That is a HUGE moral question though.
If they did resort to their tactics, they would be no better than the Klingons. They would no longer be able to claim to be "good" at that point.
If both sides are just as bad as each other, it means that the Federation is only "good" because they are the protagonists. However, since it is in part their choices and actions that make them good.
Ultimately, if I am in the mood for "kill 'em and take their stuff" ... I play unalligned (formerly chaotic neutral). I have a character in one 4e game that is effectively LN. Ultimately, that is the "protect the city at all costs allignment." I like the unalligned characters and often have them do the right thing for the wrong reasons ... and the wrong thing for the right reasons.
If you are going to have the characters have allignments, they should probably mean something. A good character, especially lawful good, would probably have some kind of code of ethics. It's not just the ends that matter, but their means as well.
I like how 4e has gone. It's taken a lot of the mechanics of allignment out. The motivations of the players aren't just "I have to keep up my allignment" or "detect evil to see if it's ok to kill this guy."
The whole idea that it's okay to do ANYTHING to an evil creature, and that act won't be evil, seems to be a bit upsetting. In fact, evil creatures do evil things to each other all the time. So, evil is what you do, not just who you do it to.
If a player wants to play a paladin, and it's in a system where the paladin can fall, they are already putting themselves into a situation where they need to work with the DM to know what the paladin can or cannot do without getting powered down. It's not moral arguments ... it's about the paladin trying to find out what he can "get away with". Of course, the whole idea of the paladin is supposed to be a paragon of virtue, not someone looking to find loopholes in order to work the system to their favor. That's not lawful good ... that's lawful evil.
A character doesn't have to be good to get XP and GP from killing things and taking it's stuff. A monster doesn't have to be evil to give XP and GP when you kill it and take it's stuff. Good or evil, especially in a system that doesn't have magic based on seeking it out, isn't going to matter as much. If you went into an orc village and killed everyone, or only wiped out their warriors, and sent the rest packing ... the people in town will see you as heroes either way. Whether your motives were good (protect the town), evil (you just like to kill stuff) or indifferent (you seek adventure) you protected the town from orcs, so they will treat you accordingly. It's pretty much just what the party as a whole thinks about it.
It's likely a lot easier for characters to have motivations, goals, allegiances, than a vague allignment that they then have to disagree with their DM over what the consquences of the allignment are. You can have a party of "good" adventurers ... and if they are all motivated by "good" things, that's fine. If, on occaision, they end up doing something wrong, that's something their character may need to worry about, and as a good character, it may be something that nags at them. If they consistently do bad things, they may end up changing their allignment. It's up to players and DMs to discuss how they want the game to go, and how much allignment really matters.
Does it really matter, in the grand scheme of things, whether orcs choose to be evil but can be redeemed (albeit unlikely at late points in life), or they are born evil and can't be any other way, or are misunderstood and "equally good/evil" as the human/elf/dwarf/etc town they are attacking ... shouldn't really matter if the goals of the game are to save the town while killing orcs and taking their stuff. If they HAVE to be cosmically, absolutely evil ... then obviously, there is something more about the game than just beer and pretzels. It either doesn't matter, or it does. And if it does matter, than there should be a reason for it mattering. It may be "easier" to kill orcs if they are pure evil ... but then why not just have more unquestionably evil creatures, like demons and devils and undead or magical constructs? And, in that kind of game ... would there even be orc babies, let alone would be important to know that the orc baby was evil and SHOULD be killed in that type of game?