I struggle with this. My ex was a copper, I would have said he was a good decent bloke who liked to help people and did his job in truly awful circumstances. I then discovered he was shagging escorts he met through work, and when I told his senior offices (who I knew) was told to keep quiet as no good would come of reporting it. So I took it higher and reported it again, and after an internal investigation it was decided that using escorts was not illegal, and that as a police officer he was entitled to a private life. So he is still working.
Then there's a friend of his who I loved to bits, she was a fantastic copper I felt, fair and calm and you would want her there in a crisis. Then, when her relationship ended she lost the plot a bit and ended up head butting a woman she had arrested for her own safety (she was threatening to kill herself) she broke the woman's nose and split her lip. Everyone covered for her, and when they eventually looked into it, the CCTV had been destroyed.
There are amazing coppers doing an incredible job, in shit circumstances, and I'm grateful. However, in my experience, they look after their own and that isn't always in the general publics best interests.