People are just terrible, and sadly, the worst people are almost always the loudest. The people who are actually good tend to be quiet on the internet and hide in the shadows (myself included), while the trolls and cyberbullies will lash out at others. While I haven't gotten hate for being an ABDL (partially because only other ABDLs know and I don't advertise this part of me), I have read some of the terrible comments, and sadly, some of the vile comments I don't think are trolling, but genuine hatred. I honestly feel like the one thing that protects ABDLs from real hate and harassment is simply the fact that most people don't know that ABDLs exist, and that if the majority of people in the outside world knew, it'd be a much scarier world.
So yeah. People are terrible, and will hate you for a wide variety of reasons (I know of people who would hate me for every single part of me). Don't read internet comments, especially pertaining to topics like ABDL, and don't even think about going onto places like 4chan unless you quickly want to turn into another misanthropist.