"Can be sexual assault". CAN. It depends on the circumstance, and in this case I don't think it's fair to classify it as so, especially since like
@Axiomus said, he doesn't go out of his way to do it. And I never attempted to use this to justify or defend the pairing, I just think it's completely absurd to use this to label Natsu a terrible immoral person who sexually abuses anyone he pleases.
Flawed logic because like I've repeated multiple times, Natsu has little to no understanding of sexuality. It makes no difference whether or not I personally would do such a thing, because my awareness of the implications of touching private parts far exceeds Natsu's.