Keep yourself in a perfect bubble, but the actual majority if people (not the smaller more niche demographic on a place here like Lemmy) would consider any guy dating a Trans female to be gay or bi.
Your response makes it look like you think that isn't true. If you actually believe that, you're keeping yourself in a little bubble/echo chamber of the world, but you are in the minority, not the majority.
Transwomen are women. Just because you're closed minded doesn't make you right or anyone else of your anecdotal "majority". If you're a man and you're attracted to women, that makes you straight. Full stop.
They can feel act and behave like women all they want and that's fine, but if physically you were a man and needed several parts of your body surgically and chemically changed then you're floating in a gray area on how men think about that when it comes to dating. If you aren't able to see that then you're every bit as closed minded as any of the men who would have an issue with that. Full stop.
A straight dude can be squeamish about dating a transwoman, that's something different. Not everyone wants dick, I get that. But a straight dude dating a transwoman doesn't somehow make him not straight. Marten is attracted to women, and is dating one. Nothing about this indicates he's bi. What is there not to get here?