>Why is it that they are so vilified in the U.S.?

It could be connected with the number of them there. No country in the world is more litigious than than the U.S., and the U.S. breeds lawyers faster than Brazil breeds great soccer players. With at least 60,000 new lawyers graduating annually in the States, that's a whole lot of targets for scorn and contempt.
TEd's passionate defence of the profession notwithstanding, in a country that lives to sue, and with myriads of lawyers who must sue to live, the depth of the anti-lawyer sentiment in the States seems unsurprising.
I also wonder if there isn't a significant component of self-loathing in that anti-lawyer sentiment. Perhaps there would n't be so many greedy, unscrupulous, manipulative lawyers if there weren't so many greedy, unscrupulous, manipulative clients. I actually quite enjoyed Grisham's King of torts for its examination of this side of legal ethics (or the lack thereof).
Finally, just to provide another target for spleen, a friend who spent his entire working life in the oil industry (another increasingly reviled sector) told me recently that the only professional group he views with universal distrust and disgust is real estate vendors. He said that in 35 years, in both the US and here, he has yet to deal with a vendor with ethics.