Many many of my hipster friends are poly, to one degree or other.
'Err on the side of safety' isn't a good legal axiom to follow. If that were the case, many rights would be curtailed. ex. Drinking...
Are you confusing polyamory and polygamy?
I didn't say it was a legal axiom, but it's what we do... rights are curtailed all the time in the interest of public safety.