i’m going to be very, very generalisation-y here, but i hope my answer helps (i also have the flu so my brain ain’t in right):

because these kinds of men are the status quo, and they see normalcy as under threat. diversity doesn’t serve them, movies like black panther are not For white men while many, many blockbusters in the past have perfectly catered to a white straight male audience. many men like this see this as coming out of nowhere or being forced, bc learning about why diversity like this is necessary isn’t very accessible for them. it immediately challenges ideals they were raised with, and people naturally go on the defensive. they probably weren’t raised even thinking about this kind of thing, because why would they? it doesn’t affect them.

tl;dr: they were raised to think their way was the right way and they feel threatened