There was a time when the need for unions and collective bargaining was indeed away to get away from the abuses from the bosses/companies/ corporations/employers who took great advantage over their workers...but like many such remedies, once they achieved power, the very people who gave aid to the oppressed, begin to abuse their purpose, and became the abusers. Some unions are necessary, some are not...some are for the workers, some are for the union bosses. Unless they police themselves and weed out the 'bad eggs', and not abuse their original purpose, the corrupt ones will(and have) cast a bad shadow on all of them.
I believe that has happened..and if not corrected will leave many innocent union workers and bosses vulnerable to an anti-union bias, which in turn has a snowball effect and discredit the legitimate ones.
Unions are NOT the problem...but CORRUPTION within certain union leadership has given unions a bad name. ...which, in turn, is making it harder, and will weaken them.
NOTE: This post is NOT anti-union...but anti-corruption and anti-abuse, by some unions.

GfS