The basis of the MythBusters argument is that a wire rig only simulated the 1/6th gravity in a vertical direction. On a horizontal direction it does not simulate 1/6th gravity. This is a curious argument, because why should horizontal movements be slowed on the Moon? If you throw a punch why should it be slower on the Moon's surface?
Yes, it certainly is a curious argument. I just don't think that it's one that they're making. First of all, gravity doesn't work in the horizontal direction, so it should be irrelevant. Secondly, bulky, pressurized space suits will tend to slow down one's movements. Third, one tends to move a little more slowly and cautiously when dealing with a significant amount of mass in a very low gravity environment.
The fact that this was filmed on a US Naval base and there are American flags everywhere also works against their credibility.
Why? I only saw one or two American flags and the low gravity rig was made and operated by a trapeze company.
One will notice that they tried the wire rig and the slow motion tests separately, declaring that they don't look right, but didn't combine the methods. This was an obvious slip up, and it is clear that they didn't combine the methods for the obvious reasons that slow motion would successfully simulate slow horizontal motion and the wire rig would successfully simulate vertical low gravity.
Then feel free to film your own low gravity rig in slow motion and let us know if it looks any better.
By the way, what did you think of the 1/6 g vomit comet results?