"He attacked and killed an evil. He did the right thing." -- With full knowledge it comes at the risk of endangering well-meaning guards who would stop him now or later.
--You, like crafted, keep thinking of the guard as a mob, "knowing" what he will or will not do. That's flat out wrong. He is a good aligned person just like you are, and makes a choice. Nobody knows what anyone will do. You know as a player, ooc, but the character does not, and that makes all the difference. Did you try to talk to the guard? Convince not to attack? Outlanders do it all the time, turning guards. Again, you know that's a cabal power, but your character doesn't, he just knows that they are people and people make choices. Your character did nothing wrong, and knows nothing at all about what others will do for sure one way or the other.
"Someone else decided to flag him according to their own personal system of laws, and the paladin neither controls nor decides when that happens" -- Is he so thoughtless he cannot have foreseen this outcome as a possibility?
--it's a possibility, but so are a lot of things, and he has a duty to kill that evil. and again, maybe they won't flag him, maybe it's a paladin or some other good aligned tribunal, or even some corrupt evil, or any number of possibilities, and he won't get flagged. The point is that he is doing his duty. And being flagged is nothing wrong, there's nothing about being flagged that is evil or bad. And once you're flagged, so what? If people decide to attack you, that is their free will choice. He can try not to kill any good aligned who decide to attack, but that is their choice, not his, as noted above.
" He did what he needs to do." -- If what he needs to do is kill evil, at any cost, including killing a well-meaning guard who would seek to bring him to legal justice.
--Except again he didn't go kill the guard, the guard came and attacked him and died immediately. That's entirely the guard's choice and fault, no blame rests with the paladin.
"If others then do things, then they do things, but it's not his fault, any more than it is his fault that the guard (who as Isildur pointed out you are entirely ignoring and considering as an ooc mob not as a sentient being) decided to attack him." -- Really? He's not the cause of it? I'm completely certain that if he did not break the law he would not have been warranted and it would not have happened. Is it not his responsibility as a paladin to think ahead for the sake of others?
--That's because, again, you are using your player knowledge, not the knowledge of the character. And, again, there is nothing inherently wrong or evil with being flagged. You continue to demand the paladin take responsibilities for other's actions, which in and of itself is often considered evil, as you are now denying others free will.
" Frankly, why shouldn't the *guard* be dying for attacking a good aligned person?? It's the guard's fault, twice!" -- Because it could have been avoided, but apparently it wasn't worth preventing.
--It could have been avoided if the guard didn't attack. Period.
"Can the paladin feel bad about it? Obviously. Should he try to avoid killing goods? Naturally. Is it his fault when goods attack him and die due to no fault of his own? Nope." -- I don't see how you can buy that. That is like if I went vigilante, killed a rapist, then the police sought to bring me to justice, assaulted me, and were shot and killed. That's not my fault even though I know there's a chance I get caught and that might happen?
--Except the real world and the fake world are, you know, real or fake. In the fake world, people not only get to kill, but are lauded and prized for it, in their causes. He got the flag because he was doing the right thing, doing what he is supposed to be doing. What others do as a result is their choice, and they bear responsibility for the consequences.