They began by hacking websites and doxxing people for fun.
However, a subset of the group split off to pursue a nobler goal of upholding people's rights and obtaining justice for those wronged, in their eyes. It was the trolling and mass information rollout on Scientology.
The creator, moderators, and janitors of 4chan have created rules against any illegal images, with violators permanently ban.
One recent attempt to protect minors was /soc/ and /b/ removing any teen, "jailbait", or questionable age threads.
But again, such content is acceptable on almost all of 4chan.
Discussing pedophilia fantasies, questioning its legality, retelling their personal stories, forming support groups for pedophiles, and venting anger towards people that do not understand their "sexuality" can easily be found on any of the mentioned boards.
Posting hentai of loli is permitted, allowing artists' renditions of child porn to be freely available.
Pedobear was an iconic symbol for the pedophile subculture in 2010.
Views sympathising with Aryan supremacy, slavery, race-tainting, inferior races, Social Darwinism, genocide, and general mocking of black people can easily be found on any of the aforementioned boards.
/b/, /pol/, /v/, /s/, /hc/, /h/, /u/, /soc/, /mlp/, /r9k/, /tv/, /cgl/, /lgbt/, and /gif/ are where the majority of sexist posts are made.
But as with racism, it is found in every board Topics of rape, male dominance, female incompetence, hatred for feminism, “perfect wives”, and teaching woman how to behave can easily be found on any of the mentioned boards. /b/, /pol/, /s4s/, /wsg/, /fit/, /adv/, /lgbt/, /tv/, and /v/ are highly ableist.
However, such sentiments are normalised in almost every other board. You can find discussions of the "antics" of disabled people, mocking, abuse stories, and death wishes.
That leaves potentially millions of privately owned and operated websites that no one has officially classified or “indexed” (such as what Google and Bing do by crawling public websites), and perhaps only a handful of people have actually seen.