You can't have it both ways. You were the one saying voting third-party was a perfectly justifiable way for Republicans to show displeasure with their party. Now you deny it has any effect. Gimme a break.
If a person is disastified with the Republican party and refuses to vote for them any more, would you rather that person stay home, vote third party or vote for the democrat?
By your logic, staying home or voting third party is the same as voting for the democrat - it's not.