<human>: I (27/F) have a really good friend (32/M) who we will call Sam. Sam is married (8 year relationship, 1 year married) but he and his wife have little in common. He and I share interests so we hang out time to time, go to movies or conventions or shows. Every time he invites her and every time she declines because she just doesn't enjoy his interests.

Recently, when he and I went out, I found out the wife is referring to me as "his girlfriend" (in a snooty way, far as I can tell) and if I text him, she will ask, "Oh, is that your girlfriend?" And apparently the topic has come up among her female friends that they will "beat me up" for her. (We are all in our late 20s to early 30s, I mean come on people, really how mature are we...?)

Sam has related some relationship woes to me but I've never swung way or another. Honestly I've just offered him a female perspective that has really helped him to understand his wife more and why she may act the way she does sometimes.

I'm dating someone, have been for awhile, and Sam and I have zero interest in one another sexually. But for some reason whenever I talk to people about this, I always get the, "Well, married people just aren't friends with people of the opposite sex" response.

Why the heck is this? Is it really impossible for people of the opposite gender to have platonic relationships?

Can you give me the gist of the text in a nutshell?
<bot>: feel like I'm a bad person for having a married male friend, why is it not okay for a married man to have female friends or a married woman to have male friends?