Well, there's basically no legal way that that kind of information is in the databases accessible via his car computer, so he's already lying by saying "you don't like police" and "it says that when I pull up your records." Police also protect their tools with a fierce secrecy, so they don't just banter about what they can access on their computers, especially when that would mean they're revealing functionality or data that doesn't have a compelling government interest, unless they're lying about it.
You can step it back up yourself by turning the question around: by what mechanism, process, or law would your opinion of the police appear on a screen in a police car?
In my book, as far as surveillance or internet comments (etc.) information getting used at traffic stops goes, that's an extraordinary claim begging for extraordinary evidence.
Ancillary links:
Difficulty of retaining a wide spectrum of information:
These days law enforcement agencies partner up with firms like Clearview[1] that mine data on individuals from the internet and build digital dossiers on them.
A story about someone getting their mined information from Clearview made the front page of HN[2] last year.
It is entirely possible that such firms are running sentiment analysis on social media posts, or analyzing likes and shares, to profile suspects as "anti-police" or not.
I'm not sure exactly what kind of mechanism they have to track such information, but some departments clearly do keep tabs on people who are vocally hostile towards police.
take a look at this video if you have a minute. dispatch explicitly warns the officer that the guy has said threatening things about police on social media. unfortunately, the encounter ends in a (very likely) unjustified shooting of an unarmed suspect.
The "warning" was based on an "officer safety bulletin" that was issued in response to Instagram posts, which I'm willing to accept was the result of a complaint (possibly someone namesearching for "MPD," we don't know). The police actually visited and interviewed him before determining that there was no threat. The original notice was rescinded and reissued saying he wasn't a threat. I haven't been able to find more detail, but it would seem the dispatcher took it upon themselves to relay the original bulletin. :shrug: It'll come out in the transcripts.
It seems to me that--unless you have other info--the police weren't tracking people so much as acting on complaints. I think we can conclude this was not information that appeared as part of the car computer, since the dispatcher thought it necessary to add to it.
I have issues with the idea of "officer safety bulletins" based on Constitutionally-protected activities, but that's a different story.
