When you know its a troll but still downvote because fuck it

No. If you want to correct someone, please be sure to know your definitions.

Cognitive dissonance is a process inside the observers mind. In this example it goes something like this: ‘I believe all cops are bastards’ vs. ‘I met a cop and he is not a bastard’ -> something doesnt match, thats the dissonance.

My sarcastic comment hinted at the person OP met not being a cop, but the flipside of a human that is a cop in their job and a completely different person in their freetime (like schizophrenics). This makes the second statement ‘I met a cop and he is not a bastard’ untrue and resolves the dissonance.

When you realize that the cop on the job and the person in their free time are 2 separate, almost independent, personalities, the cognitive dissonance goes away.