I've heard the argument from the CCW minded people that OC makes you more of a target to criminals.
Sure, that's why all of those cops in harness are singled out by criminals . . .
Put yourself in the mind of a criminal who sees you OC. His first assumption is that you are a cop. He knows that if he shoots a cop, his life is likely to be short and eventful.
If he decides that you are NOT a cop, he then has to wonder if anyone around you is CCW (or if he missed seeing an OC), because why would you just be walking around OC . . ?
Then he finally figures out that you are not a cop, there are no other likely carriers around . . .and then the question is whether attacking you will succeed.
Somewhere in that process, he will have begun considering the fact that anyone OC has probably done more practicing than he has . . .
Criminals are LAZY, not STUPID, and none of the factors above would make them eager to open the festivities.