Argument with friend [fixed]

My friend came out as trans (FTM) to his boyfriend, and the boyfriend ended up breaking up with him. It wasn't because he was trans, his boyfriend respectfully right away used the correct pronouns and would refer to him as his new name and is every very supportive of the LGBT+ community. My friend showed me the texts, and the reason his boyfriend broke up with him was because that he explained that he was straight, and was not attracted to other guys. The boyfriend tried to remain friends with him, but he was too mad and stopped talking then and there...
I told him that I didn't see anything wrong with it since her ex wasn't gay so of course he wouldn't date a guy, but he kept telling me that it was wrong of him to do and that it was transphobic and homophobic 😥
Who's in the right and who's in the wrong? I'm so confused 😪
Edit:
I had to delete it and reupload it, because I realized I used the wrong pronouns for my friend

Vote below to see results!

Glow Resources

Let’s Glow

Glow is here for you on your path to pregnancy

Glow helps you navigate your fertility journey with smart tools, personalized insights, and guidance from medical experts who understand what matters most.

25+ million

Users

4.8 stars

200k+ app ratings

20+

Medical advisors