I do practice martial arts, I have taken some hits, and i'd like to note this fact that women don't seem to grasp: A hit to the groin really doesn't have any major effect for maybe twenty, thirty seconds, possibly more. If you're relaxed then sure, it's pretty immediate, but any attacker is not relaxed. Under those circumstances, all you feel is a dull, minor ache for about half of a minute with the knowledge that you really need to finish whatever mayhem you were doing before it actually starts to hurt.
It's also a difficult target to hit. It's behind legs, and any stepping is probably going to close it. All you have to do is turn your front toe inward and it might as well be behind your rib cage.
Confidence and the knowledge that one is capable of fighting back are more important than false theories of where to throw a dainty kick, probably before falling down in apology for hurting them. If you don't act like a victim, you don't look like a good target, and they'll look for someone else who isn't a risk.