That's a very outdated standard. There are many women who are stronger than the average man, and strength isn't the only factor in a fight anyway. Besides, if a man fails to block a blow at a certain target, his strength advantage will be severely reduced if not neutralized.
To look at it another way, if a woman knew martial arts, the law would never consider that as a reason to forbid her to pull a gun based on this standard, especially since she may have no idea what else that guy might do. So, why apply that standard to a man?
Usually the standard is a reasonable person standard - how would a reasonable person under the circumstances defend himself/herself. Again GENERALLY, women are physically weaker than men but as always there are exceptions.
I have a female cousin who is 6’, 200lb and threw the discuss in the Olympics this year. I would love to see this perv try something with her.