We have to separate issues in order to have a rational discussion. If someone talks about equal rights for African Americans, it is assumed that they mean "African Americans who are not otherwise unusual in some unrelated way". So someone saying "but what about African American terrorists?" is pointless - equal rights implies that an African American terrorist be treated like any other terrorist.
Similarly, equal rights for trans persons assumes that trans terrorists, trans-rapists, trans-children etc are treated like terrorist, rapist, or children.
The question is whether being trans in and of itself changes how someone should be treated.
To answer your specific question: a trans rapist is a rapist because society has decided that a certain set of actions count as rape.
No one is arguing that ALL behaviors be tolerated, rather they are arguing that those behaviors that do not directly negatively impact others should be tolerated. Rape impacts others so it is NOT tolerated. Homosexuality does not directly impact others, so it should be tolerated. Same for trans people.
There are of course a lot of grey areas where behavior has *some* impact on others, but I don't see any significant impact on others from someone being trans.
On your other comment: Trans age is a request to be treated DIFFERENTLY (eg like a child) not a request to be treated the same way. Same for trans species (though if someone wants to self-identify as as dog, but still act like a human in all ways, that's fine with me).
I think it really is pretty simple: Does a behavior cause significant harm to others? If not, then its OK, if so, then its not OK. There is of course lots of valid discussion on what is or is not "significant'.
They are part of the "trans community" and are completely related to trans gender. Every argument in favor of trans gender is being used in favor of trans age and trans species.
What is the difference?
What if they don't identify as a rapist? Who are you to label them as such?