Because it wants you to think cops can be fun, lighthearted, open minded and progressive people who do a good thing for their communities. It's subconscious, and the NYPD has promoted it before in order to make themselves look good. I don't think it's especially effective propaganda but it's definitely not there to make the police look bad.
They also tend to lean into jokes that criminalize things that shouldn't be criminalized, namely sex workers.
pretty much my take.
i think it's just a hard pill to swallow for a lot of people. they want this show they really like to be the exception and ignore that it's part of the problem. and sorry, just because an episode here and there with progressive messaging doesn't make it all okay. if every single episode were like that? if that was the purpose of the show? sure, we can dissect it and debate whether it overcomes the propaganda it unintentionally puts out there, but currently it's a far cry from being on that level. at least in my opinion, and apparently many others.