At the risk of being the one who sounds like a broken record "being uncomfortable" with RPing with a certain gender is NOT an excuse. "Being uncomfortable" is a reason people give that sounds better than the real reason they don't want a certain gender partner. I think my favourite part about this conversation so far is the steadfast inability of people to volunteer a real reason.
You're uncomfortable because...why? Because you're a dude and you don't like the idea of doing sexy RPs with another dude? This is some subtle way of adding #NOHOMO to your list of rules? Or is it because you genuinely don't think a female is capable of playing a male character (or vice versa)? That's not an excuse either, because now you're making assumptions about my abilities without even knowing me.
Would it be okay to add these to my preferences:
-No black or brown people, I'm only "comfortable" writing with white people. (Read: I'm racist and if you Skype call me my Nazi flag will be on the wall behind me.)
-No fags/lesbos. (Read: Sorry, I can't risk sexy times with characters played by non-straights because I need to know there's a possibility your jollies are getting off on our RP.)
- No Muslims or Jews. (Read: Once again, I'm racist and also a bigot.)
- No cripples or spazoid autistics. (Read: I'm an ableist fuck who can't handle the thought of my RP partner being neuro-divergent or blind or in a wheelchair or something.)
- No fatties. (Read: This actually matters somehow because I just hate fat people.)
Did you like all of those? Then why is "Male partners only" or "No dudes" okay?
-No dudes. (Read: Because I'm a dude and I don't want to think that my dick is smaller than yours.) <- This is pretty much what I put in the blank when I see people say "I'm uncomfortable with writing with other men."
((This also brings up an interesting point. Why is it only straight people who do this? I have never met a gay guy on here who was like 'No, I don't want to write with chicks for my MxM plot' or a lesbian who was all 'No, a guy can't write a F for my FxF'. Straight people, get your shit together.))
What have you been smoking? It is perfectly natural for a man to want to roleplay with a female and for a female to want to roleplay with a man. Hell, a gay person may want to roleplay with a person of the same gender. It is none of your business, maybe they plan on having a romantic angle and they are just uncomfortable if they had to roleplay with a person of the same gender. So, what? You're not forced to roleplay with them or forced to interact with them. It is not remotely about roleplaying abilities, you can be an amazing writer but someone might not want to roleplay with you because they want to roleplay with another gender.
Also, if someone doesn't want to roleplay with someone based on anything, it's their choice. As ridicilous as it is to compare religion, disability and race to wanting to roleplay with a specific gender.