What @frog said is spot on in regards to my wife's cousin; the first thing he did when he saw the pride flag was go, "haha gay" because he's and edgy teen. And when we were talking later, he absolutely sounded like a right wing anti-LGBT+ troll, because he didn't have either the vocabulary or mindset to do otherwise. But he was asking questions earnestly.

There is tons of 'casual transphobia' in young male spaces (and casual bigotry in general), and someone has to be willing to wade into that bog if we want to pull those kids out of it. I'm not saying that has to be you or any other person in particular -not everyone can or should put themselves in that position- but if all transphobia is universally only met with hostility, even when the context of the conversation might otherwise hint that this is not someone who is a lost cause, it will drive those people further into the clutches of the Right.

That is why I brought up the lack of a Left-oriented outreach pipeline for young men; they've been ignored by the Left for long enough that their spaces are very hostile to LGBT+ people in general (looking at my fellow gamers), but we need to start clawing them back, and that has to start with not immediately treating them as lost causes worthy only of derision when they exhibit transphobia.

Many of them are just parroting the language and behavior of the spaces they occupy in order to fit in, not actively choosing or attempting to be transphobic.