Critics tend not to believe in the scream. They think they're being manipulated and they don't like it. Nobody likes to be a sucker, critics least of all. The more the critics witness the public’s adoration of Bacon's work, the more they smell a rat.
Arthur Danto, writing on Bacon for The Nation back in 1990, summed up the feelings with his typical intellectual incisiveness.
So … these depicted screams seem to entitle us to some inference that they at least express an attitude of despair or outrage or condemnation, and that in the medium of extreme gesture the artist is registering a moral view toward the conditions that account for scream upon scream upon scream. How profoundly disillusioning it is then to read the artist saying, in a famous interview he gave to David Sylvester for The Brutality of Fact: Interviews with Francis Bacon, “I've always hoped in a sense to be able to paint the mouth like Monet painted a sunset.” … It is like a rack maker who listens to the screams of the racked only as evidence that he has done a fine job…. We are accordingly victims ourselves, manipulated in our moral being by an art that has no such being. It is for this reason that I hate Bacon's art.
There is nothing worse, in Danto's eyes, than a scream that means nothing. It amounts to the destruction of the moral realm in the name of aesthetics. The key scream painting in Bacon's oeuvre is probably “Study after Velazquez” (1950). Bacon takes Velazquez' famous “Portrait of Pope Innocent X” (1650), in which the Pope is a study in cynicism and power and transforms it into one of his blurred, terrifying, screaming heads. The impulse is always to explain this, and other screams through personal history or politics. Bacon was reacting to the horror of his times. Bacon was reacting to the horror of his family life and his later relationships (with their sometimes violent and destructive characteristics). Bacon was reacting to the repressive atmosphere in England regarding his homosexuality. Danto, I think, is correct in rejecting this kind of reductionism. So was Bacon. When asked about his interest in Velasquez' famous Pope painting, Bacon replied, “I think it's the magnificent color of it.” He also stated flatly that, “I have never tried to be horrific.” Danto can never forgive Bacon for this sleight of hand.
But Danto, and by extension many other critics, miss a key distinction when they focus on the meaninglessness of the screams. Bacon retreated to the language of pure painting and aestheticism in order to resist the specific meanings often attributed to his works.