So why not let those states use their freedom to sink their own ship. If they do really have it wrong and you do really have it right then that will show and they'll come around in the long term.
Because human rights are important and oppression is bad. States aren’t monolithic entities. This isn’t a case where people suffer the consequences of their own choices. It’s a case where some people suffer the consequences of other people’s choices. You’re proposing to allow millions to suffer indefinitely, hoping that those who rule them will eventually change their mind.
This is been tried already, and it didn’t work. What changed things was force, first military, then legal.
Not arguing that it isn't better. I'm arguing laws don't always change things, and it probably isn't as good as you think it is (unless you live in a south deep-red place and know first hand, I'll take your word for it over what I've read). Actually, I'd argue that they rarely have the impact we'd like. I'd argue a lot of Jim Crow still exists, even though it is illegal.
Things are far from perfect today, but the current situation is a huge improvement. Informal segregation persists but it’s a lot better than the formal kind. Slavery persists in prisons but the vast majority of slave descendants are free. I haven’t seen any “colored” sections on the train lately, or “colored” bathrooms or water fountains.