Militerized local police vs extremist US citizens

The FBI considers “sovereign-citizen extremists” to be a “domestic terrorist movement…”.    (think Timothy McVeigh...) Many rational Americans are concerned regarding the militarization of local police departments that are increasingly use armored vehicles and SWAT teams to abduct individuals suspected of violating petty laws.   Reading city news report one can find that occasionally innocent civilians are killed in crossfires or their private property unreasonably damaged without reimbursement by these 'law enforcement' operators. 

How are these two trends related?  Is the fear of citizen extremists pushing law enforcement toward a military mindset where justice and the rule of law are secondary to police short or long term missions and their individual security? Or, are citizens increasingly angered by overzealous police tactics and unreasonable laws working together to diminish cherished American freedoms and risk the security and property of innocent civilian?