I (32M) and my girlfriend (30f) went looking for engagement rings over the weekend and I'm planning to propose soon. She's a teacher so we're looking at a summer wedding. I mentioned this to my sister and she was really excited for me. I mentioned that we were looking at some venues, and there's this old plantation that we really like in our area that may be the winner.
My sister really didn't like that because plantations are a "symbol of slavery and racism", and that it'd be really insensitive to get married there and it's offensive. I told her she was overreacting and she kept pushing the issue. So I told her to get off her high horse and quit the virtue signaling and she hung up. AITA?

NTA - your wedding, your choice.

I do find it funny, however. A couple months back a black actress purchased her childhood home - a shack on an old slave plantation. And everyone was all for it - because she was going to erase the negativity and fill it with love.

So buying property on a former slave plantation is wonderful because "the only way to erase negativity is with love" - but the same people will call you racist for having a wedding there.....

probably because the actress is black whilst the OP is (I'm assuming) not black?

Does that matter? Isn't love, "love"?
The plantations have an ugly history. You could, of course, proclaim this offensive and push for the remnants to be left to rot. But then the ugliness remains. Or, you could overwrite the ugliness by turning them into a place of happiness and joy.
People today go around looking for things to be offended by. And when they find something, they proclaim it loudly in order to get their 15 minutes of fame.
The unfortunate side effect of this attention whoring and virtue signalling (aka "tattletaling") is the destruction of history. No one person or group is all good, and no one person or group is all bad. But the tattletales focus only on the bad, and destroy the good along with it.