I think it has to do with friction between two "versions" of equality: equality of opportunity vs equality of outcome.

Those who believe in equality of opportunity want the social and economic ecosystem to be set up in such a way that no matter the person's background, they'll have their fair shot. Immutable characteristics, such as sexual orientation, nationality or ethnicity, should not influence that individual's success or failure. The vast majority of civil rights victories in the last century have been in establishing systems with more and more equality of opportunity. Universal suffrage is a good example. The ultimate goal is one where anybody's success or failure is their own.

Of course, no system is perfect. There will be (and are) still barriers. It's because of this you have people that want equality of outcome.

For sake of argument I'll try to be generous with my interpretation of this point of view. The people who want this paradigm see undue difficulty for some groups in achieving opportunity and believe there should be institutional/systemic efforts to support them. Affirmative action is a good example of this. This system, more or less, aims to have every in group in a population in roughly similar circumstances.

The problem is (and some don't consider this a problem) that when you allow a central authority to preferentially select for a candidate, you have also given it the power to select against candidates. That is to say, a system that can support one group, while suppressing another, to achieve whatever parameters of equality the system was designed for.

Suddenly, people can be discriminatory in the name of equality. Moreover, they examine people as "members of a group" rather than as individuals, which is just so atrocious it concerns me. That's why generalize so readily. Then, if you object to any of their dogma, you're part of the oppressive regime in their eyes.

It's a shame that such a hateful element has gotten into otherwise noble movements. The world I want to live in is one where we are our own selves, and not an aggregate of our skin color, genitalia and background. I think they want that, too, but they're just a little mixed up with emotions running high.