If he had voted, would anything be different at all?
If you had abstained, would anything be different at all?
Voting doesn't gain you anything, and abstaining doesn't lose you anything.
On anything but the smallest and most local of levels, it's nothing but an irrelvant distraction.
So why bother?
If everyone who voted Trump as the lesser of two evils had abstained, then we would have President Clinton. If everyone of my mindset had written in Rand Paul, we'd still have President Clinton. I don't see what is so hard to understand about that. I think there is a malicious, subversive element in conservative circles trying to convince them that voting is pointless.