Boyfriend like to tear his nails

Chingsin • 25
I was talking to my boyfriend about him preparing for his job interview tomorrow and found out that he doesn't use nail clippers but instead tear the part out slowly. What's worse is that he's been doing this his whole life and he thinks it's totally okay even though his mom doesn't approve it, only because he'd clean his hands first so it shouldn't be as gross as how others do.
I don't know why but hearing what he said and the way he acted made me flip, I got so upset that I don't even want him to touch me if he keeps on doing that. (Mind that he's turning 27 next month)
Sure everyone has a bad habit but this one to me is something that usually gets corrected during childhood. I have a friend who bites her nails whenever she's stressed but that's not the case for my boyfriend.
Am I really overreacting like he said?