It wasn't a rage fuck. His bf was bi and didn't think he cheated on Ian cuz he was with a woman. Ian took bad advice from Lip and he didn't just drop Trevor. Ian was confused Mickey broke out of jail and understand that Mickey and Ian probably loved each other since they were kids. Ian went back to Trevor and Chicago cuz he wanted a stable life.
You're just so negative you wanna run with the worst case scenario. Ian wasn't transphobic he just was never exposed to it before. He knew very little about it. Ian might be gay but that doesn't mean he knew everything about the LGBTQ community. It was very realistic considering the fact he's a poor south side kid.