OP said she didn't get your point, not that she didn't get your joke.
It's perfectly clear OP did not understand the joke, as it is clear that you did not.
Trans is more than just cutting off a "johnson" as you put it.
I didn't put it any way. I referenced another poster refering to adding a Johnson, not removing one.
And is there really any need to make trans people the butt of yet more jokes (they've been marginalised for years).
You clearly don't understand the difference between the subject of a joke and the target. The joke may have referenced the subject of sex reassignment surgery but it was targeted at the double meaning of the previous posters comment. In essence it was a pun.
Abuse of someone for who they are is bad, but suggesting an entire group cannot be referenced in humour because some people are mean is silly and patronising to the group in question.
Are you trans @whatausername? Or are you just claiming we are marginalised snowflakes so you can police others humour?