>>People can improve over time and if you're bad to them now, they may be bad to you later. <<
Dronak makes an excellent and very true point with this. So I'll toss another suggestion out there, for potential future use. Do you know any of the other men at these dances, preferably one who is generally recognized as a "good" dancer and who is tactful? You might ask him to intercede on your behalf. I am assuming here that you have a pretty consistent set of "regulars," so that most people know each other at least slightly -- that is, your friend knows the victimizer at least by name? The friend can approach the "V" and in a friendly way, work into a conversation (ot necessarily in order) that some of the ladies have complained about him for reasons x, y and z, to the point were some have been physically hurt. The ladies admire his enthusiasm and creativity in the dance. They would like to see him continue coming to the dances, but perhaps after he went to a studio for a few lessons, asking the instructor to work especially on x, y, z?
I have on occasion been approached to have such discussions. With proper care and tact, no egos get bruised, no names are used, the lady avoids any social awkwardness, the "V" gets praise as well as being told there's a problem that needs fixing. And since at most places (that I'm familiar with anyway) women far out number men, you possibly nurture a man into being a better partner, rather than having him drop out because "no one will dance with me there."
When it's presented properly by some one generally held in respect, I've found very few people seem to have problems with "constructive criticism." The ladies can approach such a man without concern of besmirching the "V," because a good dancer will probably have already noticed the heavy leads for himself while watching and "taking a breather" (or has been told about it by other women).
Ladies, however, need to ask the friend explicitly to do this, however: it's the Mars vs. Venus thing. If you don't the guy will (and should) assume you are just venting a bit, and not asking for a "fix" of the situation. An oblique suggestion is not likely to overcome a tactful man's resistance to the possibility of being a "busybody" sticking his nose where it doesn't belong.
At least, this is the etiquette I was taught for social dancing. I hope it helps.
R