From a man's perspective, we have have been taught since early childhood that hitting a woman is wrong, and I think that is a good thing.
We understand your desire as a woman to train with someone who is going to push your limits so that you will learn more, but doing that is in conflict with something deeply engrained in us. No disrespect intended at all. It's just the way we've been brought up, and it's hard to suspend the instinct to go lighter when training with women.