The analogy to bestiality is absurd, and it’s counterproductive to even bring it up.
Not so with polygamy. The constitutional case for overturning state laws against polygamy is very strong, especially now.
The strict scrutiny test definitely applies, since the bans are motivated, at least in part, in animus against certain politically unpopular groups, such as fundamentalist Mormons and Muslims.
So the question is, are these bans narrowly tailored to support a compelling government interest? Ultimately, the answer judges will give is probably yes, which means that courts will uphold polygamy bans.
The reasons given will probably be that polygamy potentially harms women and harms men by reducing the pool of mates. Since it might hurt women and women are seen as underdogs, this is a politically acceptable argument that will appeal to judges.
Even so, I think the legal case against polygamy bans is very strong, because it’s clearly motivated by bias.
Regardless, analogies won’t help much in convincing people to oppose toieva marriage, and they can hurt. Other lines of argument need to be emphasized (and tested on focus groups!)