If "No one owes you anything," then you also owe nothing to a society that works against you, including allegiance, civility, or pacifism.
A society in which it's everyone for themselves, that refuses to care for one another, is no society at all. Then everyone acts shocked and horrified at someone who understandably snaps, like modern western culture doesn't run entirely on schadenfreude.
That was the crux of the idea of a social contract, which is long dead in the US. Now people line up to revel in the suffering of their fellow citizens with "well you were stupid to do xyz in life, so you deserve your suffering haha."
Because you deserve to live in a world where people are decent to each other, and "people" includes you, and your behaviour is the first thing that's most easily controlled by yourself.
Because my conscience doesnt create constant alerts notifications and warning messages that disrupt my sleep and bother me constantly while awake if I dont try as far as I can to be a decent human being. Some people seem to have these alerts etc disabled or the entire conscience app disabled or not even installed to start with though, I cant imagine how they get though life otherwise
I find that reading some crime stories in the news about some genuine pieces of shit shuts that voice down pretty effectively. Gives some perspective and reminds you that there are far far worse people in the world and that you are merely a flawed human as opposed to a malevolent, hateful psychopath that relishes in the pain and misery they cause others