The fact ''we'' try to mental gymnastic the girl's alleged age as being ''but in X where she is from she's at least the local age of consent'', is already quite bad. We shouldn't need to do that for a relationship of which the oldest of the two is in their twenties.
There is no excuse or defendable argument to be made for a dude of 21 to be in an as I understand actual relationship with a girl of allegedly approx. 16 year old. Legal age of consent or not, we are still talking about an adult with a minor in such a case.
Because they aren't drama queens.