It’s not a matter of being ok with another country abusing their neighbors, nor is it about ‘letting them do what they want’, it’s about acknowledging the mutually assured destruction established during the cold war and having to reckon with the fact that there are other nations with the ability to end civilization that have other ambitions than you.
Leftists get mocked a lot about their pie-in-the-sky economic goals, but at least they have an intimate understanding of international conflict and the reality of oppositional superpowers. Unlike sheltered american adolescents who’ve never left their country for more than a week and have been assured their entire life that the US is the most powerful and moral nation on earth.
And that’s to say nothing about the fact that america is the antagonist to most other nations on the planet.