It happens and you will get used to it. Wave or give them the bird, it depends on my mood at the time. Most of the time they are just looking for laughs at your expense and will do no more harm than that.
If they are throwing things at you, on the other hand, that is assault. Get their plate number and turn them in.
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Cat 2 Track, Cat 3 Road.
"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --
the tiniest sprinter