Having grown up with one of my Dad's best friends being in law enforcement, I knew most cops were good guys and I could trust them. However, I was also taught from a young age to not completely trust anyone, not even law enforcement. I was taught the same thing about teachers and staff at school. Never trust them completely. Listen to them, do what they say, don't talk back, but never completely trust and if I was unsure about anything they said or made me do, to talk to someone I did trust about it. I teach my daughter the same thing. Respect authority, but do not just blindly trust it.
It's really the same for law enforcement as it is for everyone else in anything else. The vast majority of people are good and there a few idiots out there that give the rest a bad name. Just like these house parties that get busted. You have lots and lots more house parties that fly under the radar and nothing bad happens. Every once in a while you get some idiot who blows it out of proportion and makes the whole scene look bad. Does that mean you stop trusting all house parties and never go to one again?