heretohelp,
You wrote: “Only if A and B are similar. Nobody reasonable thinks that marrying a dog is similar to marrying a person, even if the person is a toievanik.”
The issue is not whether A and B are similar in an absolute, compare every aspect sense. The issue is whether they are similar in the important sense used as a basis for arguing the acceptance of A in the first place.
The Supreme Court struck down anti-sodomy laws in Lawrence v. Texas because such laws were based primarily on moral disapproval, and moral disapproval, where there is no actual injury to society, is not sufficient basis for telling someone they cannot do something they wish to do.
In that sense, which is the important sense in this case, sodomy and bestiality are very similar.