Trans logic #1 is, a trans woman is a woman. If you don't agree you are transphobic (this appears to be the default and accepted norm nowadays). Seems harmless enough but it is a bit of a gotcha as it leads to trans logic #2
The next stop in trans logic is if the trans woman is a woman (which you've agreed too), and you refuse to date them because of that alone you are breaking rule #1, you dont really believe a trans woman is a woman, so you're transphobic.
Penis you say, as per logic #1 if a trans woman is a woman then their penis is a womans penis, otherwise you are breaking rule 1 and you are a transphobe again.