Inter alia, yes. But the step from "rationality is supposed to reduce X" to "I will act as if X has been reduced to negligibility" is not a valid one.
Well, isn't that a good technique to reduce X? Obviously not in all cases, but I think it's a valid technique in the cases we're talking about.
Certainly, as you say, not in all cases. I don't see any very good reason to think it would be effective in this case. Apparently you do; what's that reason?
If there's such a small chance of your vote making a difference in the election, you should be comfortable voting for trump.