Simply logic. Cops can be corrupt but it does not follow that all cops are corrupt. To believe that you have to dehumanized a person to the extent that they are no longer human but an object or symbol. You know nothing about the cop that was killed. Did he have a wife? Children? Was he a good honest man? You don't give a shit about any of that. He's not a person to you. You're no better than the abusive power you claim to despise. You're actually worse because your a hypocrite.
Corruption happens not because of corrupt individuals, but because good people do nothing. So by proxy, regardless of if police are participating in corruption, by their very inaction they are complicit in it, they are partly responsible. Nobody is going to shed a tear over a Policemen getting killed, the modern Police force as a collective do way more harm than good and they are no better than anyone else, do you give a fuck about the many truck drivers or miners killed each week, of course not, they were just doing their jobs, and with all dangerous jobs comes risk. As grown men, they chose that risk.
You cannot be a good honest man and a police officer, that is a contradiction in terms, if they were good men, they would either speak out against corruption or leave the force. You can't join a corrupt criminal organisation and claim to be a good guy because you don't participate in corrupt activities. Your association with this group makes you an accessory to the crime. A truly good person would literally go crazy in a corrupt organisation such as the modern day police forces.