My reaction to demon dicks Fen-style is based on how they were depicted in the old character viewer, which if the memory burnt into my synapses serves, was a purple penis covered in boil-like protusions.
This isn't so bad, is indeed somewhat similar to how imagined fanfir dicks. The issue of "fleshy thing covered in nodules = diseased" still exists for me, though. I can of course see how they might be enticing to vagina havers for the extra sensation element, and perhaps therein lies a delicious erotic tension, of something strange and innately *wrong* looking, providing intense pleasure. It's just something as a non-vagina haver I can't really get into; I can only think how little I would like an abscess or a pimple on my dick.