The great thing about taste is that it can be so various, meaning that if you have trouble with someone like Dario Argento, it doesn't matter, because he is still going to have a lot of fans who will be blind to your objections.
I've never found Dario Argento films fully effective, however; although I've not seen them all. Of the ones I have seen, I find The Bird with the Crystal Plummage the least objectionable; and contrary to what I've just said, despite an ineffectual first seventy five minutes, the end is highly effective - minus the psychobabble postscript, which is straight out of Psycho anyway. It's a great ending, with a good surprise, some quite horrific ideas, and some truly crazed acting from Eva Renzi.
Mario Adorf has an unusual, and actually unimportant role in the film (it's immediately obvious he is too short to be the murderer); but he plays a wild-haired and eccentric artist. It's one of these scenes that you may forget from the film and true enough - cut it out and the drama will not be effective.
That doesn't mean it's not a great five minutes of Mario Adorf though; he is earthy and comic, mature and yet deranged, and playing the temperamental artist in a typically horror-buffo kind of way. I've a freeling that the end of his scene has been cut also, but it is good to see him with this crazy hair, character acting for all he's worth; it's a shame that the character bears little close relation to the rest of the film. I'm sure the character must have originally had great purpose in the director's mind, but lost something in the realisation - I think it sometimes happens with Dario Argento.