Sexual orientation and bestiality are two different things......your family's beliefs are your business, for nobody to judge.
The concern is more that your stepson is physically abusing the male dog (after all the dog can't consent to this activity) and correct me if I am wrong, but I seem to recall you writing that you suspect Sal may have inappropriate thoughts/intentions toward your own infant and another very young relative if I remember correctly.
This goes way beyond sex play and experimentation. Sal appears to be, and I'm sorry to be so blunt, a potential predator in the making. That to me is the real issue, that he has already taken advantage of a (helpless, unable to consent) animal and you have a fear he may be thinking the same about babies in your home.
You may have to go it alone to protect your younger child and the pets....I hope you and your H can come up with a plan.
