I was averse to going down on women when I was younger and less experienced. This was mostly because roughly half of the women I'd been with at that time weren't very hygienic-- there was an undeniable odor as soon as her panties came off.

Nowadays I'll go down on her if she seems hygienic since I want her to have a good time and come back for more sex down the road. I always have the "STD talk" before I have sex with a new partner and I keep my most recent STD results on my phone for their peace of mind. I've never had an STD in my life (knock on wood)

The dudes paranoid about going down on women because they think she's a whore are probably not cut out for having responsible casual sex.