It may be a useful survival trait in some sense, but it's not useful in others. Often I run into situations where people lose their heads over something that is not a real issue.

"EEWW!" "Oh, the bucket is full of maggots? OK, let's go dump it in the woods." "Oh, I couldn't possibly do that! EEWW!"

Or people will freak out over some feces or urine, and stand around discussing how disgusting it is rather than just cleaning it up.

I imagine doctors have similar opinions about normal people and blood (not a reflex I've had much luck with controlling consciously).

More importantly, this is a kind of mindfulness meditation, which generalizes - if you can step back from maggots or feces and ask yourself 'is this really something to be perturbed by?', then surely you can do the same for many other issues. (I have read that sometimes Buddhists or Hindus would meditate in front of rotting corpses, but that's probably taking it a bit too far.)

Feeling revulsion about things seems like a useful survival trait.

I'm not planning to lose my sense of revulsion any time soon, only to become able to ignore/suppress emotions when they're not useful, like when deciding on a charity to sponsor or whether to eat revolting celery or non-revolting cupcakes.

Controlling your emotions is probably better-taught by participating in an adult- literacy program, or voice-only technical support

Horror movies are entertaining, and if you have cardio equipment you can easily do 2 hours of exercise painlessly while watching one. If you already use spaced repetition, it might take at most 10 hours total over the course of your lifetime to get a hundred shock pictures and rate the due ones daily for how much you flinched when you saw them.

The first option in particular seems orders of magnitude more efficient than spending hours answering boring tech-support calls for low pay.