I have a problem with police depts militarizing but I also find it humorous that some of the worst violators of the nfa registry are in fact those same police departments.
The thing to keep in mind is the sudden transfer to individuals that will occur without a central government. Those weapons will be walking out the door in the hands of many officers that will have no intention of doing anything but protecting their family. There may be some nice hardware on the market shortly after a collapse.