plpol, but tbh it is general pol too
Not voting or making invalid vote is neither a fight against broken system nor a moral choice.If both options trully suck, and there is no lesser evil, you still should decide for minimal damage option.
Not voting is somehow seen as the "moral option", because you refuse to vote for someone bad.
But you did not, in fact, refuse to vote for them. Essentially it's giving both of them a vote, giving an advantage to person that might fuck you over more than the other.
The system is broken. But lack of valid vote IS participating in it.