I consider a wee Christian fish badge on a car a sign to handle it with care, as the drivers of same tend toward the lower end of the driving skill/ highway code knowledge/ cyclist friendly pool
If I seen that coming, I'd get myself into the next county sharpish.
(Anecdotally. In my time, I reckon I've nailed the "problem road users by decoration" thing quite well. Basically, anyone using a car as an advert for their beliefs or a fashion accessory is best avoided. And pretty much anyone in a Hyundai Accent, small Vauxhall vans, brightly coloured french hatchbacks. And definitely any business-sponsored SMaRT, MINI, Fiat 500 or suchlike. By comparison, the perennial bugbears of motorists, like Beemers, Mercs, SUVs tend to stay the fuck away from me. Perhaps I look like my sideburns would scratch their paintwork).