I think folks should avoid making generalizations about large groups of people, including police. There are many I do not like, and some I do not mind, and others that I consider friends. As far as protecting each other goes, that can often be the case. On the other hand I personally know of two officers in this area that were charged with DUI after being pulled over, and this was not after an accident. The officer that arrested them certainly could have brushed it under the rug, but they did not. I am also aware of another local officer that was charged with reckless driving due to excessive speed, I believe it was 120+ in a 55. All three officers in question lost their jobs, as they should have.
Don't get me wrong, there are many cops I really, really dislike, but I find generally if you know the law yourself it is not really that much of a problem to avoid trouble with them. In general I just try to avoid law enforcement that I do not know.
This situation sucks, it is horrible three people lost their lives due to a drunk driver, and really bad that the person responsible will not be charged because of screw ups.