Why is it such a crime to like this movie?

Honest answer? Because most people enjoyed the movie, and the tiny percent that didn't are outraged by that. They can't separate their politics from their ability to enjoy art, and they lash out in rage. They organize campaigns to down-vote the film on Rotten Tomatoes and flood boards like this with whiny posts.

The Last Jedi is an okay film. Like most films it has its ups and downs. It gives us some unexpected twists and turns, all the while staying true to the groundwork laid by the original trilogy. At other times, it falls prey to a lackluster reliance on CGI and action set pieces, a fault many modern films, including the original trilogy, are at times guilty of having.

If you really want to see a whiner rage uncontrollably against the film, remind them that Rey is probably the most fleshed-out, well-developed character in the entire Star Wars canon outside of Darth Vader, and that her actions and abilities follow the rules and precedents set in the prior six films. They can't accept that truth, and will instead sputter about Mary Sue's and red pills and men's rights until they turn blue in the face.