Whether you think it's a good or bad thing depends on your point of view. The TPP is very complicated, and it was negotiated behind closed doors. Some people didn't like it simply because of that. They believe that policy should be made in the open, not in the shadows.
There were two main things that the TPP did that caused a lot of controversy: it streamlined trade between signatories, which is great if you're a business owner or a consumer (because it drives down the cost of goods and labor) or a worker in a country with high unemployment and low wages (I'm talking Bangladesh here, not the U.S.). It's not so great if you're a worker in a country with high wages like the U.S. because free trade tends to drive wages towards being more uniform, so if you're in a high-wage country you can expect your wages to go down, or to lose your job altogether.
The second controversial provision was stronger enforcement of intellectual property laws, often allowing corporations to take unilateral measures against alleged infringers that bypassed local laws. The allegation was that this provision effectively turned multinational corporations into de-facto governments, thus undermining democracy.
These are the main reasons the TPP was very unpopular in the U.S.
The argument in favor of the TPP was that the status quo has a lot of problems that need fixing (which is true) and that the TPP, flawed as the process and the result may have been, was our best shot at fixing them (which may also have been true).
It is constitutional to join treaties that otherwise undermine the constitution, the nation's autonomy, sovereignty in general.
Negotiating any treaty behind closed doors, let alone seeing encroachments on discretionary rights like intellectual property in the various leaks, should be met with skepticism and determent.
In addition to what was said, it also was an important piece in containing Chinese domination of the region. It would bind the nations into an international order that was not subject to (or strongly protected from) Chinese leverage of influence. Now China is much more free impose their will by threatening the economies of their neighbors.
There were two main things that the TPP did that caused a lot of controversy: it streamlined trade between signatories, which is great if you're a business owner or a consumer (because it drives down the cost of goods and labor) or a worker in a country with high unemployment and low wages (I'm talking Bangladesh here, not the U.S.). It's not so great if you're a worker in a country with high wages like the U.S. because free trade tends to drive wages towards being more uniform, so if you're in a high-wage country you can expect your wages to go down, or to lose your job altogether.
The second controversial provision was stronger enforcement of intellectual property laws, often allowing corporations to take unilateral measures against alleged infringers that bypassed local laws. The allegation was that this provision effectively turned multinational corporations into de-facto governments, thus undermining democracy.
These are the main reasons the TPP was very unpopular in the U.S.
The argument in favor of the TPP was that the status quo has a lot of problems that need fixing (which is true) and that the TPP, flawed as the process and the result may have been, was our best shot at fixing them (which may also have been true).