Society is changing very quickly in some ways (not quickly enough for some, I admit, but too quickly for comfort for others) and I think men are facing a lot of questions about the "role" (for lack of a better word) of men in society, in the family, etc., etc. Some find this evolution of gender roles very threatening, and men especially - having traditionally been breadwinners, authority figures, head of the family, etc., etc. - might have a tendency to be more threatened by anything or anyone who reminds them that their role and place in society is very much in flux. A man transitioning to a woman I would think would be very touchy for some men. Like - "Wow. If John could suddenly decide he's Jane" (not saying it was sudden for John/Jane, but that it felt that way for others) "what does that say about me? Am I who I think I am? How secure is my manhood?"
I grew up in a single family household. I was an only child, my mother was the provider. In some ways that changed my expectations of gender roles in ways that a lot of my contemporaries, who still grew up even in the 70's with dads who worked and brought home the bacon, and moms who stayed home and cooked it, didn't experience. And because of that I didn't always fit in with the guys. I'm very secure in both my manhood and my heterosexuality. And yet, over the years, I've often found it easier to relate to and be close to female friends than male friends. Probably because of that I was often called things like "faggot" when I was a kid and I was often subjected to bullying. I do think part of that was jealousy because I often had some very pretty girls as friends that I spent time with! (Maybe not "girlfriends," but close friends.) But I think a lot of men have still grown up with that very traditional family structure with very defined gender roles, and they feel easily threatened by anything that threatens to change those things.
