He spoke of the fact that promised side agreements on the environment and workers rights never happened.
In 2005, he spoke in detail on problems when Ron Portman was going through confirmation hearings, referring to not just the problems here, but the problems in Mexico.
When CAFTA was being written, Kerry fought for a provision that the AFL CIO endorsed which was narrowly defeated in the Republican dominated committee. He spoke in committee of the opposition to CAFTA from the Bishops in Central America and referenced studies that showed the damage done by NAFTA in Mexico.
Kerry voted against CAFTA. I don't think he supported later Bush agreements.
I think that there could be an honest debate on whether trade deals could be used to correct the problems that globalization itself causes. Note that the problems Michigan faced started, not when NAFTA happened, but earlier when new auto plants were built in the non union South. Over time, what happened is that international corporations, which the car companies now are, have gone to using cheaper and cheaper labor. In essence, globalization has completely destroyed the balance that unions had given workers in making deals with large employers. Globalization expands the potential labor force. The question is how to deal with this. Though they have NOT done so, it might be that trade deals could be part of the solution to the problem caused by globalization.
Obama in his earlier trade bills did include the provisions that NAFTA lacked. Kerry did support them. This is not an issue where progressives would agree with Kerry.
Where a HUGE difference existed between Kerry and Dean is that Dean argued for over a year that Kerry was wrong to negotiate with Iran.