So, umm... what's /b/? 
/b/ is to 4chan what 4chan is to the rest of the internet, it's 4chan's General Discussion, it's the source of 4chan's
power reputation
4chan.org/b/ (it is NOT safe for work (or home unless you pay the mortgage), that not being a link was very much on purpose)
4chan, and in particular 4chan's /b/ has a reputation for being the darkest most edgy horrible place on the internet, so people who want to do the worst thing imaginable on the internet go there to be as horrible as they can possibly be. and any time that it gets an unusual level of interest the regulars spam it with porn and gore to scare all of the tourists away. /b/ is the place where people who were told that they can't do something on the internet go to do it. considering that and the fact that it is often called "the **** hole of the internet", it's not "that" bad, there are places on the internet MUCH worse, though many of them are sites for literal hate groups or criminal enterprises, but there is a huge gap there.
most of the other "SFW"* boards, /a/ /co/ /v/ /x/ are not significantly worse than HLP GenDisc. some might even be more civil (thinking /sci/ /g/ /p /po/)
*not actually safe for work