It's hard to come with non-anecdotal evidence for this. You can have increasing passenger numbers, but they still may be increasing at a rate below the rate they might have if the TSA didn't exist. Obviously, it's almost impossible to know what that hypothetical number might have been -- even if you survey travellers, many of those who hate the TSA endure it anyway because they have no choice, and many of those who choose to take the train instead might have done so anyway for other reasons.

I do know that for myself, I have been willing to put up with a fair of amount of hassle and expense to avoid coming into contact with the TSA. Most of my recent visits to the USA have been done by flying into Montreal, Toronto, Tijuana or Cuidad Juarez and travelling overland to US destinations such as Boston, Los Angeles, New York and Albuquerque. I tolerate the other problems you mention -- poor customer service, lost baggage, etc. to the same extent as I would flying directly into the USA, but I don't have to deal with ignorant, power tripping TSA security screeners, because amongst all the air security agencies whose agents I come into contact with around the world, only the TSA's have these problems. That is the first and foremost question that the TSA has failed to answer, and indeed, the GAO and other studies failed to ask -- how is it that every other country in the world can keep their air passengers safe without harassment, intimidation, power tripping, threats of arrest, silly arbitrary rules, etc. etc., but the TSA cannot? To me it's such an obvious question, but yet the TSA doesn't even make an attempt at posing it, let alone answering it.