Nowhere was I saying that I don’t think straight cis ppl can be good allies, one of my closest friends is a great ally and is a cis man, sadly they are a rarity (at least in my experience). Like some of the most homophobic and transphobic ppl I have met will have a partner who is queer in a way that the man finds socially acceptable
I feel like it is bc men are more likely to become violent and aggressive. I have been told by so many men (in queer spaces and in other spaces) that they can fuck the gay out of me (even by men dating other queer women). I have been slapped in a gay bar for turning down a 3some and called a dirty dyke
For me it is more so I’m scared of violence and this is just a be aware of who you are bringing into queer safe spaces, and if a straight woman was going around behaving in this same manner, I would be hesitant of the bi man who thought it would be okay to bring her into that environment