you're missing the point.

yes, that content is despicable and probably shouldn't have been created in the first place, or at the very least stopped from publishing by valve. but that's not what we're talking about here.

if the payment processors have that much power to pull games they don't agree with, they won't stop here with rape/incest and can pull whatever they decide is "impure".

it sets a precedent where the people who handle money can grab even more power just because they feel like it. dating sims/violent shooters could be on the block next, and while it would be a much harder push for them due to the size of fanbases, would you still roll over and say "well not everyone wants to be subject to these things on their computer"?