Martha Brown has written a nice posting on a self defense class she took, and I have to say that, all things being equal, taking the course is better than not taking it. This is not a rebuttal, but something I wish to add, since real estate agents do get attacked, and, sadly, killed in our line of work.
Disclosure: I was assaulted by a client in 1998 when I was 31 and in good shape. I was a 4 year varsity wrestler. It did me no good. My attacker was an ex-cop it later turned out.
Disclosure: My college roommate and former co worker at my first brokerage is a black belt in Tae-Kwon-Do and was nearly killed in his own office. He required plastic surgery after that attack.
These attacks did not occur in dark alleys, open houses in obscure locations, or in abandoned homes on the wrong side of town. I was attacked in the client's kitchen while his wife looked on, taunting me. My friend was attacked in his office. Interestingly, we are both male, in decent shape, and do not fit the profile of the news stories about female agents being accosted at open houses.
Beating up your attacker is not plan A. If you can defend yourself, do so to the extent to get away. Think Edith Bunker when she thwarted that would be rapist. But if you fight, you are engaging someone in their turf; they were ready- you weren't. And the element of surprise is lethal.
Prevention is more important than reaction. Don't be alone with people you haven't vetted. Don't do open houses alone with no backup. Casually remark that you expect a male associate any minute.
Hand to hand combat has problems. Here's the thing: Attackers sucker punch. Attackers rely on the element of surprise. Attackers are con artists who will go out of their way to make you feel comfortable. Attackers wait until you turn your eye away. Then, they'll hit you hard, fast, low, and repeatedly. That's the problem. They play dirty. They never tell you to put up your dukes. They rig it to their favor. Sharks, for example, don't attack on land, where they aren't very tough. They get you in the water. Don't go "in the water."
If there is going to be a battle, make it a battle of wits. You can win that one. If you are alone in a house with someone who makes you uncomfortable, say "Greg Nino will be here any minute with that survey I forgot on my desk," or "Jeff Belonger is running late but he has some great financing programs for this house." Then, get on the phone and call Greg and Jeff and say "Hi, I am at our open at 927 Elm, there is a man here who really want to see that floor plan/mortgage/survey." They'll get the message. If I got that call from one of my team I'd send Cavelleria Siciliana.
There are tons of things you can do to avoid a scrap. Get names. Get numbers. Verify. Let people know where you are at all times. Work as a team. Carry mace or pepper spray. Keep your eyes open and keep your distance. Never be alone with an unknown out of distance from civilization. Casually mention that others are on their way. But it is prevention, not a good left hook, that is the best deterrent to being harmed.