There's nuance. Obviously, vote for the liberal over the fascist, it's not even close. However, the fascists are absolutely represented in government, while there's no leftist candidates to speak of. Leftists have to plug their nose and vote liberal, while fascists gleefully vote republican.
Voting is entirely for loss prevention, because ultimately it absolutely impacts minority groups and people who stand to lose a great deal by a republican victory. However, leftists will not be able to move America to the left by voting.
That's why grassroots movements and building up of parallel structures are so important for leftism, it cannot work within the confines of a 2 party Capitalist state, and must be built from the bottom up.