We all know about the Pillow Talk during the sales process, but the truth is in the "AS-IS" disclosure which is what you're going to battle in court. $2,000 will get a couple letters passed back and forth with their attorney.The sentiment is that way because the OP asked about legal liability. The dealer charges more because they have significantly higher overhead costs than a private party. People pay more for the reasons you cite - that dealers have the facilities and knowledge to check out the car and sell them something that has had qualified eyes look it over. That doesn't mean that they do, and it certainly doesn't mean that they are legally liable.
Does it mean they're crappy? Well yea, but that wasn't the question. What the dealer 'owes' is a matter of negotiation, as OP is clearly not going to use them in the future and already has damaged their reputation. If 'owes' is bound by the law, they probably don't owe anything, as the sale was as-is. If 'owes' is bound by good customer service, then they probably should compensate some how, but it sounds like the OP should already know what to expect based on car condition and the fact that they never returned his call.