
In fact, a lot of douchebag, predatory men deliberately cultivate and groom women as partners and friends to be their beards. They know that they look more trustworthy with a woman to vouch for them, so they go out and find women to vouch for them.
Not only that, but the assumption that a douchebag stops being a douchebag once he convinces a woman to date him is basically making women be their man's keeper. It assumes that she will keep him in line. There are even songs about women making men Walk The Line. We have an entire culture built up around insisting that women police their menfolk and keep them in check. Stop making women be the keepers of men. Make them grow the fuck up on their own.
And also, here's a newsflash for you: WOMEN CAN BE PREDATORY TOO. Not having a penis (because all of these kinds of rules pretty much associate genitalia with gender) does not prevent someone from being a predatory douchebag.
Two of the worst manipulative abusers I've ever met are women. But they both get held aloft in the poly community as leaders, invited to speak, their writing passed around as Truth, and asked to organize events. Why? Because they're women, so if they cry "abuse" first, we all have to believe them automatically, even though crying "victim" is one of the most common tools an abuser uses to isolate their victims from their social support network.
And no one is allowed to name them publicly, one of which because she managed to orchestrate a gag order on her victims, and the other because of the issues with victims going public, so to protect her victims, she remains a Missing Stair that we all have to whisper about in PMs and face-to-face conversations. Hell, even doing that is fraught with danger because someone warning someone else about her, if the person you're warning is a POC, risks you getting accused of making POC do your own emotional labor, or something.
If they were men, in today's political climate, we could name them publicly and there would be backlash. But we can't, so they go on about their merry, abusive ways.
My point is that none of these "no single men" rules actually protect your groups from predatory behaviour. "No single men" only ensures that your predators are harder to spot because they've manipulated the system with a layer of protection behind women champions, and "single men pay a higher price" only ensures that your predatory people have yet another layer of privilege on top of everything else because they are *wealthy* predators who can afford the extra money.
"No predatory behaviour" is what protects your groups from predatory behaviour. If that happens to make the single men demographic a little thin on the ground in your group, then so be it. But then the single men who *do* pass the bar are going to be quality people. And you might be surprised how many partnered men and how many women end up getting weeded out too.