I agree, and I never suggested that unions should be banned or otherwise prevented from existing. I think unions should have a right to exist but shouldn't necessarily be propped up by legislation that gives them the upper hand in negotiations (e.g. anti-strikebreaker legislation).

I think unions are positive or negative on a case-by-case basis. Given the value of human life, safety-critical industries almost always benefit from union presence but Hollywood for example seems to take on unions as a burgeoning cost of doing business without them providing much in the way of real value. I don't think they're universally good or bad.