I think there is a difference between someone being afraid and being repulsed. You can know in your head that you are not going to be hurt, but if something freaks you out - whether it's bugs or snakes or having gunk dumped on you - then it freaks you out and makes you shake, squeal, etc. There is a lot of middle ground between believing someone really thinks they're going to be hurt and that someone is acting their response. It's like I'm not phobic about spiders, but if a spider scuttles in the corner of my eye, I will flinch and probably yell, but I'm not really frightened of them, and once I'm over the shock I'm fine about the spider being there. It's like an instinctive response you can't control. I think the most believable reaction for most things is that you'd struggle to do some of these disgusting things the first time but then you'd adjust and be OK as the trial went on. But some people are genuinely phobic and won't adjust.