I feel like Father/Son roleplay might be more taboo even if you only look at how gay males used to be thought of as pedophiles though i believe society has made a lot of progress toward male/male relationships, i feel like, for example people would be offended by father son porn
Meanwhile Mother/daughter has been a very present thing in porn for a very long time now, Mother/son wasnt really extremely taboo in porn either and father daughter same thing. All these seems to be MOSTLY accepted without too much issues
The results so far don't actually surprise me all that much. It'd be interesting to see the results if each could be rated on their taboo-ness, though. Just because some aren't seen as being *as* taboo as others, I'd be curious to know how much less since the margins may be slim.