Ask HN: Why is it a big deal that FTL violates causality?

As far as I can tell, FTL allows you to send a message in such a way that you can receive it before it was sent. But how would that allow me to create a time paradox wherein I can cause myself to not be born? My naive brain doesn't see how this constitutes "real" time travel where I can go back in time in my current reference frame.