The GOP has always hated unions. Whenever they need a villain or a scapegoat, America's unions are always at the top of that list. Never mind the fact that union actions help increase wages across the board, even for those who aren't members, the Republican Party just can't stand the thought of letting workers collectively bargain for better benefits.
The failures of the "Big 3" had nothing to do with union workers, as the GOP has been saying. It had to do with the fact that these industries didn't adapt to the times, and continued making dinosaur gas-guzzlers that Americans couldn't stop buying. It also had to do with the fact that CEOs like Rick Wagoner were pulling in millions of dollars a year (in Wagoner's case, about $14 million) and losing billions (around $40 billion for Wagoner.) CEOs were being paid for failing, and union workers are now taking the blame.
Before you think that unions played a role in this mess, ask yourself these questions -- Did Bear Stearns have a union? Did AIG have a union? Did Fannie Mae or Freddie Mac have unions? Did Lehman Bros. have a union? No, they didn't, and yet they still failed and we still bailed them out.