From what I understand, it's coming from a place of promoting a safer community by banning source material that may be controversial for whatever reason. Some communities ban entire fandoms while others cherry-pick certain characters that have been deemed problematic.
It's not really an approach that I always agree with, at least not to the extent that I often see in recent years, but I can also definitely understand the mindset in this day and age!
not to be That Person, but I'm gonna go off on this for a sec
while yes, some sources can be problematic in the sense it's a very sensitive/uneasy topic (looking @ you, Diabolik Lovers,) pulling from these works doesn't necessarily promote the topic at hand/equate to the person who pulls from said source to approve of things. in a sense, I think of it as extremely gatekeep-y when people won't allow certain characters/fandoms because
as long as they're handled maturely, I don't see the issue.
to block off allowance of certain topics takes away from the option of playing out of one's comfort zone and becoming more in tune with writing a variety of topics with thoughtful prose. if it makes someone uncomfortable, they simply don't have to read it. most of us are adults (although we can argue that some don't act as such, not calling out any folks in particular,) so naturally we can differentiate character from writer.
but if we're going to bar certain sources though, that pushes us into the topic of whether or not it's an appropriate course when it comes to banning finer details like mental illness, drug abuse, physical/sexual abuse, and other more uncomfortable topics. this is really just me pondering on this instance, I'm not really looking for a debate, just kind of pointing out how backwards it comes off as to me in the fashion of a different point of view.