Various responses

As far as viewing Lolita, or any work for that matter, from the details to the general and not vice versa, I agree with Leah's explanation. Students, literary critics and many other readers have been "trained" to think that certain symbols are universal across most, if not all works. It's sort of a cop-out technique, and it's very flawed. What if, when watching Blue Velvet, someone thought "Well. There are a lot of blues and reds in this movie. This probably means that the characters are conflicting with sadness and anger," and left it at that? Starting from scratch with the details is effective because it allows you to enter the author's world with a blank slate and no pretenses. If that same Blue Velvet viewer began with the details from Lynch's world rather than prior symbolic knowledge from ours, it would become clear that evidence suggests that the blues and reds represent much more. 

As far as the vulgarity of Lolita goes, I'm having the same issue as you, Glo, but I'm not so sure that mine has to do with some sort of pedophilia immunity, but rather the structure of the text. Nabakov does such an awesome job of sucking the reader (or me, at least) into H.H.'s world, that you almost feel empathy. I began to really dislike the characters that he disliked, just based on the way that he described them. I began to shrug with a possibility of agreement when he used past noble figures as justification for his infatuation with nymphets. And when everything seems to be going wrong for H.H., it gave me a sort of anxious, impatient feeling. 

Blue Velvet tells a story from an unbiased standpoint, making Frank's actions foreign and unjustified. Tropic of Cancer may be from Miller's vantage point, but he does not feel the need to justify his actions- he just does what he wants. Lolita, however, seems to serve solely as an explanation of wrongdoings utilizing whimsical language to evoke readers' emotions rather than hard evidence and a coarse plot. This may be why it comes across as less offensive.