I think the worst "Am I the A-hole?" posts are ones like this one, in which (mostly) dudes take a hard stance and execute a performative gesture that they believe makes one point, even after many, many people tell them that their actions do not have the effect they think they do.
If you have to start your post with, "Title sounds very bad and horribly racist, but let me clarify," chances are things are not going to end well for you. This guy is right about one thing; the title, "AITA for banning my brother from bringing his Indian gf to my wedding," does, in fact, sound horribly racist.
He wants to clarify, though, so we'll let him. He writes that his brother has been dating an Indian woman since last year and explains that her parents do not approve of him. They don't like the relationship because he is white.
This makes OP mad. Sure, it's not great that his brother's girlfriend's family has a problem with him. Sucks for his brother. Sucks for his brother's girlfriend. But in my opinion, this isn't quite OP's problem. He can absolutely be there to support his brother, but there's not much else he should do about it.
But he can't just let it go, and he decided that, since the girlfriend's parents don't like his brother, he won't like the girlfriend, and he decided not to "accept" the girlfriend or invite her to his wedding. Thinking he was being considerate, he sat down with this poor woman and explained that he couldn't invite her to his wedding if her family wouldn't be nicer to his brother, and that "she will be banned" from all future family events unless her parents change their behavior or she disowns them.
You heard that right. He's holding this woman accountable for her parents' behavior. The logic... It's so backward... I can't... There are no words. Obviously, she got extremely upset, and so did his brother. Even though his goal was, ostensibly, to support his brother, he made things worse for his brother. Point blank.
It boggles the mind how he thought this was a good idea. He's thinking of it with an "eye for an eye" kind of attitude, but it simply doesn't compute. And commenters were not afraid to tell him how off-base he is.
"'In order to punish your parents for how much they hurt and isolate both of you, I'm going to hurt and isolate both of you the same way.' Who thinks that way?" one person wrote.
"YTA and you are a racist. How will being sh--ty to your brother’s gf help him be accepted by her family? It’s so odd because you can see why her parents are sh--ty but you cannot see your own s--ty-ness. Stop being sh--ty. First graders know that two wrongs don’t make a right," another very blunt person wrote.
OP tried to explain in an edit to his original post that he was "NOT doing this to punish her or her family." He feels that she is "toxic" because she still hangs around his brother and his family even though her own family doesn't approve. Has he never heard of children defying their parents' wishes? Has he agreed with every single stance his parents have ever taken?
If he truly has no problem with the girlfriend, he would embrace her and understand how hard it is for her to openly defy her family. Openly loving someone her parents don't approve of isn't toxic; in fact, it seems quite the opposite.
Also, there's no world in which his rejection of the girlfriend makes her family come around to his brother. As one commenter explained, "I'm from a family that's not only Indian but also Muslim.
"The one thing that got some of the more prejudiced relatives to eventually give in to accepting the relationships of those of us who went outside the faith / ethnicity for partners was realizing how petty they looked in comparison to the loving, accepting other family."
OP responded to several comments, making it clear that he, um, really doesn't get it and is probably actually very racist. At the very, very least, he doesn't understand how being a supportive person or constructive human interactions work, and I'm sorry that his brother and his brother's girlfriend have to deal with him at all.