This is the first time in 72 years that they are looked at this badly.
As a result, unions are no longer just alienating Republicans. As Gallup points out, independents have now begun rejecting union activism in large numbers. A year ago, 63% of independents approved of unions, but that number dropped 19 points to 44% today. In contrast, unions lost 9 points among Republicans (to 29%), and even lost six points among Democrats, dropping from 72% to 66%. Moderates have begun questioning the labor movement’s goals and tactics.
The major problem that the unions have is that they are viewed as far-leftist thugs that perpetrate hate crimes on conservative blacks. They don't seem to help anyone but themselves at the expense of everyone else. You never see them talking about down-trodden workers and they are mostly portrayed as Brown-shirts smashing heads at town hall meetings.
Add to this the hypocrisy of them pushing Post Office health care for everyone else while they sit pretty with diamond studded health plans that no one could take away. You then look back at the auto bailouts and see that they now own a vast equity share of two out of the three auto makers in the US at the expense of bond holders. I think big labor may have inflicted wounds on itself that it will take decades to heal.