MAGA.
You could say that Trump is crude and vulgar, and I would agree with you. But that's not the hat. That's the person. The pussy hats, on the other hand, are intended to be offensive, crude, and vulgar. And whereas the message of the hat may be that the situation is so desperate that a shock is needed to get people's attention, for me it actually has the opposite affect. I'm less likely to take seriously a woman with a vagina on her head.
A guy wearing a giant dick on his head would be the same thing. Somehow, though, I don't think giant dick hats would get the same sympathetic reaction that the female genitalia do.