At first glance, Boogie Nights has a very post-modern feminist feel to it. The women who work in the porno industry are not portrayed as automatic victims, and are presented with a complexity that most of the male characters don't possess. Anderson is also interested in charting the manifestations of women-hating in the culture. Anderson is a smart enough writer to make this sea change shocking. While both these scenes generate enormous energy they ultimately don't work.
Nothing here feels exploitative or gratuitous, the violence has enormous psychological resonance.
In contrast, the drug deal and robbery scenes begin to feel fake, emotionally false to the film's basic view of the world. The problem with the scenes is not simply that the violence is artistically or emotionally misplaced, but that, like sentimentality, it opts for easy and unsatisfying interpretations of complicated material. It would be easy to claim that as good as Anderson can be these scenes of misplaced violence are simply a case of his not trusting himself enough to follow his best instincts. But the problem is a little more complicated. Boogie Nights clearly wants to be about more then a pop movie about porn and by escalating the violence Anderson is trying to say something bigger, grander about America.