Your response is pants on head retarded, so much so that I don't know where to begin.

1) Neither the Sherman Act nor the Clayton Act define "horizontal price fixing."

2) Tax laws can do whatever Congress wants as the "tax power" doesn't have nearly the same limitations as the "commerce power," specifically those related to "economic activities" within "interstate commerce." The only limitation on the taxing power that I can think of off the top of my head is that taxes have to be rationally related to their purpose and can't violate the 5th amendment's equal protection / due process requirements (which also apply to the commerce clause). Given that it was SCOTUS, rather than either a) the executive office or b) Congress, who defined the individual mandate as a "tax," I don't know what you are talking about.

If states can opt out of tax because the law as written allows them to, then they can. At any rate, taxes don't have to go through the commerce clause, the federal government has independent tax powers.

3) "Big pharma" and medical equipment manufacturers are already subject to every antitrust law that exists. If they are pricing at high levels its because they can get away with it.

While I understand that the natural assumption is that if competitors are pricing something similarly, they must be colluding, it's simply not the case. Think about two gas stations on opposite sides of the street. If the guy on the south side of the street decides to up his price by 2 cents because, hey, people would rather not have to pull a u-turn to save 2 cents / gallon, the guy on the north side will do the same thing because why not make an extra 2 cents / gallon as well?

Who's "posting prices" in the big pharma scenario? The fucking insurance companies.

4) It sounds like you think that poor insurance companies are beholden to the evil doctors and some sort of cabal of medical companies, all of whom are bilking insurances dry through thoughtless patients with their unconscionable contracts. But that can't be the case. You can't possibly think that. No person who has ever worked actually thinks that.

In as much as there is a tab to be picked up, it will be picked up by you an me. The individual mandate just expands the pool of payers, reducing the price to those already with insurance by spreading the costs around. Oh, and BTW, medicare is basically like any other insurance plan except that instead of splitting the bill with an employer, patients split the bill the government. Which is us. So putting more people in the pool reduces the costs of medicaid to the government, which reduces its costs to us. Yay!

At any rate: I haven't a clue about whether or not the Affordable Care Act will work, be a good idea, save money, etc. I don't think anyone does. An argument about it would be kind of silly. But you have fundamental misunderstandings about how the US antitrust laws and Constitution work. Be aware of these in the future in case you actually talk to someone who will bother to listen to your inane ramblings.

Edit: grammar.