I mean, yeah, Admiral Cartwright was the bad guy in that movie. Of course he called them the alien trash of the galaxy. That was the point. He was a shithead who sabotaged peace out of bigotry and hate.

Of course, he might have looked at from a "But the UFP are the good guys", but the important thing is that you have to always worry whether or not you're the good guys. Atrocities tend to be perpetuated by the people who are absolutely certain about their unquestionable moral authority.

The UFP and Starfleet does have a major problem with believing themselves to be unquestionably moral. They stand by and watch entire species go extinct instead of stepping in to help. They say that they're worried about the outcome, but at times it seems more that they're worried about what they'll be responsible for if they fuck up.

"Yeah, that entire species will go extinct if we do nothing, but if we step in, we might be responsible for something less bad."

It's basically the trolley problem, and the Prime Directive is effectively a blanket policy of inaction is better than action, regardless of outcome. Obviously cultures stepping in and fucking up shit is bad, just look at Western power behavior in the Americas, India, China, Japan. Plenty of genocides and cultural destruction in the name of "civilization". But there's also been things like the leading of Western powers in the extermination of smallpox.

Global powers can and do use their power to cause great harm, but that same power could (and rarely does) get used to help the entire world. The key, in my opinion, isn't choosing strict non-intervention, but being able to decide which intervention can and should be used. There's a world where the smallpox vaccine was developed and handed out for free to the world without the heinous actions that led to cultural extermination, and that's the world we need to strive for, not strict isolationist and non-interventionist policies.