Well, it's kinda hard to put into words why people hates Blueberry, but I'll try.
You can get along with Blueberry quite well, and as long as you do, he can be a rather nice person. The trouble starts when his opinions don't meet yours. Bluberry seem to be pretty black n' white: if you're not with him, you're against him.
Punishments even for little things are harsh. It's useless trying to explain your point of view to him, he doesn't listen. Instead, you just get into more trouble for "arguing with him". Luckily most stuff on WRP server are now done by admins, but Blueberry is still in the background.