This may have been explained earlier, apologies for any repetition on my end.

Internalized hatred is real and is a huge factor in this. Many people, when they feel they are on the ‘other’ side of oppression, easily take on the role of oppressors themselves. They believe they have ‘paid their dues’ and found success, and even feel as though they are even more qualified to judge and weigh the rights and qualifications of those in their previous position. It’s very similar to the mindset of older people who have paid off their student loans and staunchly believe that student loan forgiveness is wrong. They think that since they ‘put the work into it and upheld their end of the bargain’, it somehow diminishes their efforts if those that come after them have an easier path. Our confusion lies in the understanding that this is not the direction that progress exists.

Another point, which can be separate from the above or exist alongside: it is a simple fact that being a minority in any group does not mean that person is exempt from feeling prejudice or even discrimination towards minorities in other groups and anyone else for that matter. In a world ready to categorize, divide, and split the tiniest hairs to serve that aim, its a small wonder why we see so many hurt people hurting people.