'The Beast' is a film of 2 halves, the first a pretty dull set up of an aristocratic wedding, the second is an odd mix of dream sequences about The Beast who looks like a man in a fancy dress rat costume with a telescope between its thighs.
It's odd, sure, but is it entertaining? The 'erotic' scenes includes some horse on horse action and The Beast raping an 18th century aristocratic ancestor of the main family, if you imagine Benny Hill going hardcore, then you get the picture.
As far as being legitimate art house cinema goes, it's no more legitimate than the likes of Tinto Brass or Jess Franco.
Why was it banned for 25 years? The scenes containing The Beast are very OTT and leave nothing to the imagination, it's all prosthetics of course but I wouldn't want him cropping up chasing me through the woods in one of my saucy dreams.
All in all you have to wonder what type of film he was aiming for, erotic? comedy? horror? or an erotic comedy horror? To be honest I think he failed on all 3 counts.