I think you might be painting with too wide of a brush. There are many fine men who become LEOs, although I have met a few who got into police work because of an inability to master the Fryolator 3000.
Police Chiefs are a different catagory altogether. Most have mediocre police skills at best but excel in office politics. Also, in many (liberal) cities, having a leftist political orientation is a big plus for promotion. I wonder how many police chiefs actually believe the bravo sierra they spout. I suspect more than a few say the stupid things they do just to impress the city council and the liberal voters who elected them.
Police chiefs are politicians. They say anything necessary to keep the office. That includes placating liberal city councils that appoint them or liberal voters who elect them in cases where they are not appointed. Few of them are individuals with a spine and principles. I freely applaud the minority that do have principles in accordance with our Constitution.