Every fandom has it's bad eggs, sonic just happens to be the best example seeing how most female characters are overly sexualized (ie: rouge and amy) and there exists alot of hentai drawn of them.
I think it's because of fan service seeing how fans asked for something more adult, and in return sega made shadow the hedgehog game turned which was a shitty devil may cry that had furries with pistols and machine guns killing demons and police officers
