I have found that it is very easy to "catch" most men who are pretending to be poly in order to find sex with a poly woman. A simple "What is a book about polyamory that you have read, or hope to read?" or "What's the name of our national organization?" will usually leave them flailing.
Single men as pigs, hmmm. I don't think it has anything to do with marital status. I look at online dating, whether on a poly site, a sex site, or a conventional dating site, as panning for gold in a sea of pigs. My boyfriend is certainly not a pig. My ex-boyfriend, who is single, while I could call him a lot of awful things, I would stop short of pig. I have some male friends whom I met online who are not pigs. I have interacted with people whose situation (married, not poly, cheating on their wife, or trying to) would lead me to believe that they must be pigs, and they were not at all (although I could not date them, because they were cheating). I have interacted with card-carrying poly guys who were most certainly pigs. I've met perfect gentlemen in the casual encounters section of Craigslist, and unbelievable pigs sporting very respectable-sounding profiles on OKcupid.
Oh, and the one-penis policy? Any woman who puts up with it in her relationships should ask herself, "Why does my man think it's less serious, less threatening, doesn't "count," as much when I am with a woman as when I am with a man? Could he be sending me a message that women themselves just don't matter as much as men?"
The only reason, as I see it, to EVER adopt a one-penis policy is if the couple is trying to get pregnant and doesn't want any potential questions about paternity. Otherwise, it's a bunch of controlling, sexist BS.