Aka because we're the "good" guys
Self-interest doesn't require moral justification.
For some reason I can't reply to "luddit3" below you. But he should check a list of countries that started the most wars and invasions in the last 150 years and which one tops it easily.
There is no good, just bad and kill-it-with-fire kind of evil. You choose bad you get a bad life. You choose the other you get literally hell. One government harvests and sells the organs of its healthy population[0][1][2] and the other makes some people feel sad.
Ironically, the "good" guys here allow you to talk shit on the internet about them while the "bad" guys would catch and harvest my organs someday for writing this comment.
[0] https://en.m.wikipedia.org/wiki/Organ_harvesting_from_Falun_... [1] https://chinatribunal.com/ [2] https://theowp.org/reports/china-is-forcibly-harvesting-orga...
In preventing a country from being invaded, yes, we are.
This is a common criticism in these kinds of discussions, but no, protecting oneself from foreign influence and threats does not require a moral high-ground, just as locking your front door doesn't.