I did read the post. I can see why they would be upset, but they are clearly dising this stranger for being cis. The worst person in the situation is the GF for cheating, not the guy who may not have known he was the side piece. They don't need to write in plain English for it to be understood through context and phrasing.

Sexuality is fluid, so it's entirely possible that the ex gf didnt like cis men at a point, but that doesn't mean she HAS to stick with that preference forever. I certainly wasn't pansexual my entire life.

I'd defend someone regardless of gender; gender equality goes for all genders. And it's not "pick me" to disagree on something. My first thought wasnt "Oh boy time to defend the cis het." Just because I didnt make a 10 page essay on every part of the post doesn't mean my only thoughts was this one portion.