I get that, for sure. Porn is definitely becoming less taboo though, I think, whereas incest isn't. So I think there's still a fair difference there. If you are caught watching porn, it's a case of everyone knows that loads of people watch porn, and plenty are open about it, you're just supposed to pretend you don't do it. If it's incest porn though, social convention is for them to be disgusted at you for it (even if they're actually not disgusted), and to think you're a reprobate, etc. A lot of the time, it will automatically come with those questions or assumptions that some have already responded to in this thread - "you watch incest porn, so that must mean you want to fuck your mom/sister/kid," etc.
I read the dev's post as him coming to this decision after a long time of struggling with it (and IMO, that maybe shows in the drop in quality over the last update or two). It doesn't come across to me as a sudden decision to quit the game, or a sudden onset of guilt/shame over the theme (though I could absolutely see the wife not knowing and suddenly finding out being a cause, that's definitely a plausible theory).
Obviously, this doesn't make it right, or good. Given what he actually says in his post (and not what I or anyone else reads into it beyond the actual words), I would say dev is doing the right thing, but maybe just going about it in the wrong way. We'd all like to see the game finished, perhaps even if it is a quicker ending than we might have otherwise expected.