So it's not a temporal paradox that's the problem. It's that you might accidentally commit suicide-via-time machine.

This is also nonsensical because of the grandfather paradox; that is, you can't go back in time and kill your own grandfather and thus undo your existence, because then you wouldn't exist to go back in time and kill your own grandfather. Oh, time paradox. You are fake science under the best of circumstances, and now you're in the hands of the good folks at Marvel. Blah.