As someone who had played and at times played on SL, then I cant neither confirm or deny such things are there. Yes I had seen there is some sim worlds that have that kind of stuff, but I also had seen many other kind of sex things in it, as well for a more general SFW part of it. In all honesty, I still prefer to be on an adult sim in SL as I dont have to worry about for not "being too naked" or (If some people are into that) being too "realistic" with a feral avatar. Plus I also wouldnt worry too much about swearing or something like that in the chat. But as for free, it is hard to get on to the adult sims, so you do need to be ready to offer some money for it. Otherwise most of it is moderated or general sims.There is quite a lot of bestiality in SecondLife
The problem I think for many, especially introverts like me, is to get out there to find people to talk with or to find what you are looking for. With what I learned, then it is mostly: "You find what you are searching for, if you know where to look or know someone that knows something" It can be really hard. As of writting this, I only know few (At lest one, maybe max two) sims that are geared to bestiality. I dont know any of the other that I had read in this post