And, there's your reason. They get fired up because it probably does apply to them personally. You get a dozen men in the same place, give them that information and at least two of them will get fired up because the threat detailed is them. A couple of dudes will half-heartedly sound off in support; these are going to be your mansplainers and you're boys will be boys apologists. About half the remaining men will just nod and look vacantly, not necessarily agreeing, but certainly not disagreeing — really not even seeing. With no discerning difference, that majority will similarly react to the few remaining men who understand and support women.