I'm not entirely certain what the main cause/motivation is for the militarization of the police. I do know this:
1] The militarization of the police IS happening.
The 2 major reasons, one reactionary, the other sinister are probably part of the equation, but the question is - in what proportion?
1] To increase government power.
2] In reaction to greater and more dangerous criminal violence.
Now, #2 could be used as an excuse for #1....
Ultimately, I think it is just a mix of all of it. I think, (like Jefferson did) that this is the NATURE of government/military/authority/police. It is inevitable, and you should expect it to happen. You task them with a job, that job is impossible to do to perfection - yet humans will try. You cannot stop murder, drugs and any crime which is motivated by variations in human behavior. So, as a society, we task authorities with combating human nature. An impossible goal that essentially becomes a power-grab and an arms race.
Mixed in with that, you'll get the occasional tyrant who really does lust for power and domination over regular people. You have totally hardworking, God honest people who are just trying to do a stressful, difficult and dangerous job. And everything in between.
The solution is a pro-liberty solution. You consider all the "evils" in society, and you choose to make the most heinous and disruptive ones illegal (like murder, rape etc...) The lesser ones, such as drug use, prostitution etc...you leave be. You have to weight it out. The less which is illegal, the less the police will have to do to combat it. And the less the police will seek greater and greater power.
Many things which are illegal today, were legal in the past in America - yet no problems existed. Meddlers, authoritarians, nosy people, interventionists, and generally those who can't mind their own business, whether it be because they have tyrannical urges, religious motivations, or whatever -- have pushed to make many things illegal. Some of them are in the government. In order to create more power, you must create a threat or problem, then offer a solution that increases your power. Then you have just regular American citizens who demand "there should be a law...." all the time. That very statement tells a lot about the way some people think, or have been taught to think. Others believe that what their God tells them they should impose upon you, and they use government as a vehicle to do this. It's bad enough we have government the way it is, but there are millions of Americans that demand far worse than what the government proposes.
It is all very sad.
In the end, brilliant men like Jefferson reduced and condensed this all into one great and simple equation - the RKBA. That's it. Everyone should be armed, and armed well. Being armed solves many of these problems. Most of these problems never even form or come into being when there is a heavily armed populace.
Unjustified No knocks won't happen if the community assembles the militia and pays the local PD a visit. No one would take away someone's property (Kelo style) if the community assembled their militia to persuade certain entities. Virtually every wrong in American history could have been dealt with peacefully in Jefferson's vision of an armed-citizen, militia society. They were truly the greatest political scientists because they truly knew that government was destined, even in their form, to become tyrannical. Rather than try and solve that problem by rearranging the parts, you instead deal with the source of the problem directly - force projection. Government, police, authorities...cannot tyrannize when their ability to project force is equal to or weaker than the population. Of course, this also makes their job difficult because opportunists in society will take advantage of this condition. Rather than ban effective arms (1934 GCA), we should instead ask if that should be the "price of freedom"....Unfortunately, public education and wars have destroyed a few generations many, many decades ago - and these individuals lost touch with what being a classical American was like. Since then, it has been an uncontested power-grab by the government at all levels. Today, we're not different, but we remember back and read about it in history books and dream of an America where the citizen is supreme again.
As for the topic above....I don't know. We've had threads about police pointing loaded guns with LIVE ammo at school kids in their drills and raids and "lock downs"....some have argued this is to scare them straight, or for the police to "flex" to the future criminals, or to desensitize students to a police-state. We've seen massive taser abuse. We've seen bad raids. You name it. Could go on for hours.
I know one thing. There was a time in America where schools had books on guns, kids played cowboys and indians, some high schools had rifle teams...and no one got shot. Today, schools act like, are like, and look more like prisons than schools.
If you treat children like criminals, they will become criminals. Lose the restrictions. Teach real subjects and lose the social-engineerings. Bring back the humanity. It'll work. If not, it's better than the alternative, which is more of what we have now.