Humans are resistant to change, regardless of the context. If they recast Peter Dinklage in Game of Thrones, there would be the same sort of behavior from certain people. Often times when you enjoy something, you have an intense desire to keep it from changing because change can be bad or good, while if you are enjoying something you will feel it doesn't need to change. I never really read comic books, to me the idea of watching Batman foil the Joker's plan at the last minute would stop being interesting after about 3 repetitions, however there are people who would read a comic book where Joker sets a trap, and Batman foils it at the last moment over and over if it were slightly changed each time, and because they enjoy that idea they would be upset if it were changed.
I really loved Team Fortress 2, vanilla TF2 was the best multiplayer game I have ever played. I could play 2fort for 5 hours everyday and always have fun, it was repetitive but I enjoyed it. And when Valve decided to update the game and upset this perfect balance I enjoyed I got incredibly mad. I'll bet half of the first hundred or so posts I did here were in threads talking about how shit TF2 is now. Whenever a story would post something like "New TF2 Gamemode" or something I would always comment about how horrible the game is and how I am definitely right and millions of other people are wrong. I understand now why I was so upset which lets me sympathize with other people when they get upset by changes.
Also, I have no idea how many people regularly read comic books but I am assuming it is many thousands of people, possibly millions. I have yet to see any article about a change to comic books with thousands of unique responses. When something happens that is perceived as bad for video games (blaming violence on games, Australia banning games, EA existing) there aren't a hundred million unique comments about things, there might be thousands of really angry people but that puts them in an insane minority, like hundreds of thousandths of a percent compared to the known amount of people who actually play video games.