The first: there is a major discrepancy between Zizeks popular, wild analysis that you find in his essays, paper backs, youtube-links and what not, and his theoretical work that revolves around Lacal/Hegel/Marx. Second point is his departure from and dispute with post-marxists such as Laclau and Mouffe.

His pop-culture analysis are often derived from his psychoanalytical approach to politics, but he doesn't bother explaining it, so the result is provocative and jumbled, and easy to misunderstand, as with Trump and the nazi-punch (BTW, Zizek a Bernie-guy through and through).

I think your question regarding the 'animosity' stems from the dispute with the post-marxist - and it is a theoretical, even ontological one, so people skip the hard part - the ontological differences between ie. him and Laclau, but this is the very foundation that leads Zizek to criticize 'PC'-culture.

Now, the difference between Zizek and post-marxist is in regards to their different ideas of how to re-animate the left after the fall of communism, and can essentially be boiled down to the debate between Universality and Particularity. And that is more than I want to post about right now, but you could read 'contingency hegemony universality' - a discussion between Ernesto Laclau, Judith Butler and Slavoj Žižek.