I think everybody in a democracy-ish country is responsible for their voting choice. Choosing to abstain is a valid option, and should stay that way.

However, if you have a preference between the candidates, by abstaining you are mathematically helping the other guy. That’s especially true in our two-party FPTP elections in the US.

Edit to add: it should go without saying that this assumes you have the capability to vote one way or another. You know, since we have a political party that wants it to be difficult to vote.