I have problems with people who abstained. The hard thing is, how do you change voter behavior?
Getting out and organizing strikes/protests and building third-party grassroots political movements are absolutely great suggestions;
Yes, voting isn't the only action. As a union steward, I'm well aware. People should use multiple tools, but at a MINIMUM people need to vote(as long as we remain mildly democratic).
It is the absolute weakest tool to actually enact change in the U.S. political system.
It is a very strong tool in preventing down sliding.