The supposed point in voting is that you are given a choice. You are supposed to be given a choice in voting for who you think best represents your views, the way you want to see the country governed, etc.
If there is NOT a candidate that you believe would represent your views, govern the way you would like, etc; then there is always the additional choice available to you . . . not to vote.
Not voting can be as much of a political statement as voting for just that reason. It represents the great disenfranchisement you have with the system.
Why do you think there is not a hole to punch, a box to check, circle to fill in, OR EVEN THE OPTION to write in, none of the above? Because they want you to believe there is no other option than to vote between the choices forced upon you.
That proves how much of a political statement not voting is! If it were not political, then there would be no fight to keep a NONE OF THE ABOVE option off the ballot. If it were not political they wouldn't go out of their way to void your entire ballot if you wrote in none of the above.
But because we are sooooo free and must vote or die

we are prevented from casting a vote to express dissent. Instead we are forced to not participate in order to dissent.
Anyone has a right to criticize at any time, voter or non voter. That's supposed to be what makes this country free!
To those that don't believe in political freedom even if the choice is not to choose at all.
Also
to those that believe simply voting every 4 years is the end all be all to political action in this country like 2-0-Sixx said above