At the APD hiring web site, on the benefits and salary page:
http://www.apdonline.com/benefits.html
it lists as a benefit "Tuition Assistance and Educational Leave". It also lays out how having a degree significantly increases your salary.
Such benefits are typical of government workers who collectively bargain, and for union police departments, as APD is.
An assistant chief at the Texarkana, TX, police department told me he had a degree. I asked what in. He said, "General Studies."
So he might have taken classes that interested him, or were easy, only to increase his salary. Who knows? Like at APD, his classes were paid for.
Any education is apt to favorably affect human development. Knowledge will likely lessen small minded thinking, prejudice, and increase self esteem.
But as far as cops not being thugs, things like education, who the leaders are, what the training is, who the mayor is, while they all may play a role in determining whether a cop is going to be a thug or not, the overriding factor is society.
When a cop walks down the street, what does he or she think his or her role is? What is expected of them?
Look at it this way. You may have an education, and not be a thug, but it's not the education that makes you use manners and be genteel so much as it is the kind of people you associate with - the norms of your society, its shared beliefs about what appropriate behavior is.
On the street, everyone's a punk and a thug. That's your peer group. That's who you play to. You can be educated and be a thug. You can be trained in something, come from a respectable family, and be a thug. George Orwell's "Down and Out in Paris and London" is the classic demonstration of how a personal devolution takes place when someone finds themselves in a meaner and more desperate set of conditions.
Society is very fractionalized, in that when you walk down any street, or into any office building, you very rarely speak to strangers or engage them in any way. Most people don't even make eye contact in public. In that context, in that kind of overall society, police play a psychological role. Furthermore, society holds the cop up as some kind of heroic archetype. Every criticism of police comes with the qualifier that there are lots of "good cops" - despite the fact that these good cops are who make up the society of police.
When society decides it wants to be kinder and gentler, it will be. When society decides US wars of aggression must cease, they will. When society decides to live under a different system, where cooperation is better than competition, aggression and violence will diminish at all levels of society, and when society decides it doesn't want thugs for cops, it won't tolerate them, or reward thuggish behavior.