Then why say it? Comes across to me like a "no offense but..."

Well, offense taken.

I'm not puritanical and neither are the clubs I was referring to. However, American culture is so puritanical that they can't even think straight about sex -- can't even talk about and don't know how to get it.

And so idiots (all of them) end up at my tabletop clubs, my hiking clubs, my movie clubs, my woodworking clubs, and then chase someone's butt the whole time.

That makes it really uncomfortable for everyone else and also usually uncomfortable for whoever's butt is being chased. And then a club has to spend social energy creating a Code of Conduct and wondering who will enforce it.

Horndogs need not apply.