I have been quite upset numerous times, like most of you. But in my life/employment I have learned that most times you CAN NOT FIX STUPID.
Pride and ego have to take a back seat to being alive.
Whether the idiot can PROVE you caused the damage is pointless - if they THINK you did what is going to happen next? Are they armed? Are they willing, cracked windshield and all, to push you off the highway with their cage? If confronted about it will you lie about being the cause of their damage (and all you were was nervous (rightfully so, yes) about their tailgating)? If so, should that not imply that you were wrong because you had to lie about it (say THEY call the cops because they noticed you do it).
I will admit being verbal a time or two when I ended up next to the idiot at a light or whatever. But anymore, I make them pass me one way or another. If they continue to be stupid I can go around them or stop before becoming part of their stupidity.
Intentionally dropping items on the road to damage a person's rig is not an appropriate response to them being stupid. It just makes you wrong, too. And if your dropped chunk of metal causes them to panic and they crash was that really an appropriate 'punishment' for being stupid? You are not judge/jury.
Sorry about the mini rant. Yes I have been tailgated many times and dealt with my share of stupid/aggressive/dangerous drivers. Yes I am almost always armed, but prefer not to go there unless they make me (and busting their windshield would kinda make some of it my fault, and that is not OK). And look at that, here I am riding today...
I am now fully prepared for angry disagree-ers to chime in...