OK but it's still the division that made the vehicles at one time. I would assume those technical specifications are still on file at that division. So even if it doesn't hurt vehicle production they will have all the know how to make both the regular and military version of the H1 as well. Of course that's assuming they didn't acquire that some other way already.
Also we are still at war. If something else were to happen (say N Korea for instance) and we needed to ramp up production there would be a long delay bringing the factory back on line. Article read the US plant only needed to stay open until 2010. That's not very far off.
There's nothing secret about the Hummer H1/Humvee at all. It's designed to be a great off-road vehicle, and that's about it. Humvees and their equivalents are used by practically every government on the face of this earth, so selling its 'secrets' to a Chinese company isn't going to hurt anyone

And the H2 and H3, for the record, were absolute garbage, i agree.