I think part of my problem is perceptions as to what sort of society the US has. It is, as far as I am aware quite peaceful except for the occasional problem area but even those are somewhat limited in what sorts of weapons are available - primarily small arms. RPGs and IEDs are not available. Although, I wonder with the return of so many veterans from Iraq and Afghanistan whether IEDs might feature more in the future?
However, leaving that point aside for the moment, one has to wonder about the devolving down to backwoods police departments these sorts of vehicles. Sure, they look cool but are they really required? How likely is a major criminal or terrorist event in such locations? What is occurring is IMHO a dangerous militarisation of the police in the US. Yes, some inner-city police departments might require some of these vehicles but does every police department? I'd suggest for most police departments, giving the police officers a pushbike might be better for not only their own health but their relations with the communities they are policing.
Then, as has been mentioned I suspect giving them away is merely the US military getting rid of a scrapping problem. Most of these police departments aren't going to realise how difficult and expensive it is to maintain specialist military vehicles, particularly as the years progress and spares become increasing difficult to find.
I too believe the US military is falling back into the view that Iraq and Afghanistan were not the shape of what today's wars are increasingly going to be like. The mentality of Napoleon's "war of the big battalions" is a strong one in the US military. They saw Vietnam as outside the norm, with the consequence they were ill prepared to fight Afghanistan and Iraq. It's a lot easier (and better for one's career) to focus on the corporate mindset than it is to consider the unusual and the difficult. Which is a shame really because the US Military had, before the 20th century a rich history of COIN warfare to draw on. Something the Generals seem to prefer to forget.
Anyway, US (and it appears Canadian) society seem to like having these things in their vehicle parks. It means of course they tend to want to use them, which means they get taken out at the first excuse and often cause unfortunate escalations in situations.
Of course, I could be talking out of my hat but thats my two cents worth on the matter.