I very rarely have an issue when out taking photographs myself, my view of it is if drivers want to make themselves look daft by giving gestures or whatever then that's not my problem, I'll still upload the photo and if their management happen to see it as dissy them then it's their own stupid fault. I won't go out of my way to get drivers into trouble though.
Of course I will always try to slow down if it's possible, to give a better chance of a shot, especially when there's traffic in front of me etc... I seem to get photographed quite a lot in Middlesbrough but half of the people I don't know so never find the photos...