I typically don't mention it unless I feel it is going to be an issue. For example if they ask me to step out of the car, I would say something. Although that's never happened to me.
I've worked with a lot of law enforcement individuals over the years, and while 99% of them are rational and decent, there are a couple of wackos with badges and guns. And the nuts don't wear a different color uniform (maybe they should).
Bottom line, if they don't need to know, I don't bring it up.