If you, be you male or female, ever touch my naughties without my explicit permission, I will touch your naughties back... with my fingernails... and PULL HARD. I will MAKE YOU CRY. Don't even go there.
If you ask my permission, you'll probably get a no, but I won't damage your reproductive organs. In this case, rejection IS in fact clearly nicer than the consequences of not asking. I honestly think one of the reasons the skeeve goes on is because in most cases, getting rejected for explicitly asking has a higher "pain" toll than just grabbing for what you want.
I know violence isn't always the answer, but think about it. If a guy grabbed another guy's junk, he'd get slugged 99% of the time. Guys don't "accidentally" grab another guy's crotch, like, ever. If guys got a similar response from invading women, don't you think the learning curve would be much smaller?
I like the idea of the "women back each other up" thing, except for when it suggests you should start invading other people's interactions if you "get a skeevey vibe". If you see someone screaming "NO NO LET GO OF ME" yes, interject yourself, but it seems like a bad idea to walk up to the low-esteem girl getting her own twisted form of affirmation from a predator - that's not a cycle you can break by telling him to go away, and you might even piss off the chick and give her more reason to go home with him. Helping her find self-value in some other way is a long process, and you can't take them all on (unless you're a therapist by profession anyway). In other words, YES back up women (or men) that ask for it and clearly need it, but don't appoint yourself the great scourge of skeevishness for all women; that's a great way to be That Guy too. Just be responsible for you. If that seems insanely easy, you're probably doing it wrong.