Yes they're wrong
Voting is a civic responsibility of everyone. Your only viable alternative is to go off and live on an island somewhere
The Witnesses make the argument that by voting, you are responsible for anything bad the person you vote for does, which is fallacious because that's not how representative democracy works. We as humans make the best decisions we can and employ others in areas we're not qualified or don't have time for. If a doctor, lawyer, architect, or engineer screws up, it's not your fault for hiring them. It's their fault for failing you. And it's the same with politicians.
Even if this were not the case, you are just as responsible for your inactions as you are for your actions. If you can do harm by voting, (I don't agree with that, but let's assume just for the sake of discussion that the Witnesses are right) then you can also do harm by not voting. If you are responsible for the bad things someone you vote for does than you are equally responsible for the bad things someone you don't vote against does.
So the JW argument fails on both fronts.