As someone who lives in a country were unions were one of the major political forces during the 20th century, the impact they had on the social and economic development is truly self evident and mostly (overwhelmingly so) positive.
Of course, the GP might be from a country with another experience.
American labor unions are closer to cartels and the setup would be illegal in many European countries; in some states you aren't forced to join a union, but you still have to pay at least part of the dues that ostensibly covers contact negotiations. In other states, you must join the union as a condition of being hired.
Contrast that with countries where unions (like health care) are not tied to an employer. The whole dynamic is very different, and I think less adversarial between unions and employees.
In the US if you have a problem with your union, you are out of luck. Make waves, and the union will make your life hell. It's a second layer of rent seeking management.
Ever since the SEIU tried to take a cut of all government benefits to families who care for disabled people in MN, it was obvious that unions here exist to serve only themselves.
Ok, fair point from an individuals view. But considering that its known that unions are a controversial opinion, it would still seem rash to state its obviousness.
Of course, the GP might be from a country with another experience.