Rightly or wrongly, I feel I have to put my tuppence worth in here.
Having had a bad experience with police in 'the land of the free', I found the clip not so much shocking as typical. Albeit, MY experience came nowhere near this guy's, and occurred at the Boulder border, I ended up refusing to enter the USA because of it.
I feel that, as Peeps says: It's been blown up out of all proportion. For goodness sake, it's only a video clip. Just one of many that can be found floating through the ether every second, ranging from mobile pictures of someone being kicked to death to children being bullied.
This is not a political forum; if you don't actually agree with something posted, you should do the British thing and ignore it - don't bring people down by treating them like recalcitrant children.