By "littered all over the Internet", I'm guessing you're referring to the drawings being found on image searching sites, and not on places like Fur Affinity.
I might not know exactly how search engines work, but I imagine they look around for keywords and stuff. So if someone looks on Google images for "Zootopia Fox" and winds up finding questionable stuff of him, it's the 'fault' of the engine getting those images from places like DeviantART, e621, and Weasyl thanks to the keywords beside those drawings.
The artists who draw those things and upload them to the aforementioned art sites only really intend for them to be found through searching and browsing on said art sites. I just can't realistically imagine a large number of us going around posting this stuff where nobody's asking for them, or perhaps doing something like Google bombing or whatever in order to get the adult content to the top results of searches. And if that really is something that some people do, how many of them are actually furries and not just Internet trolls attempting to shock people and trying to make us look bad?