Straight guy here. It's more than just social/psychological and genitals for me. The thing that's always missing from these conversations is that men and women differ in more than just their genitals and the way they act in society. Keeping in mind of course we're talking about averages, men and women have different bone structure, hair, voices, skin, smell, etc. There are a lot more physiological differences then just what's in the pants. I understand you have trouble understanding monosexuality (probably as much as I do bisexuality), but I'm not even remotely turned on by anything masculine, and I can promise it's not just some hangup about what my friends would think of me. I realize there are various options for trans people that address some of the characteristics I've mentioned but, if I'm being perfectly honest, from what I've seen it's often just not enough. It's nothing to do with my attitude towards trans people per se, I also wouldn't be attracted to a cis-woman with a strong jawline or a deep voice.