A trans man coming out as a man is never a loss.
I don’t care if he went into a male-dominated field. All fields are cis dominated.
I don’t care if he’s a straight man now. He should be allowed to be himself and happy. He does not owe it to you to be a miserable lesbian for your comfort.
I don’t care if you thought he was hotter before. His happiness is worth the price of your desire. Also you’re wrong and I’m giving him my number.
More trans men is a good thing. More trans men means more closeted trans men are feeling safe to come out. That’s a good thing.