Phew, gettin' warm here!
Uncle Jaque seems to have hit it. For better or worse we live in a society that can't live up to the Wobblies' ideals of breaking down the separation of labour and capital. Thus employers are necessary and so are unions. Neither is "evil", and each should be capable of flexibility for the sake of the commonweatlh.
I've been active in a union and now I'm an employer, and I've no regrets about either.
At the end of the day, if all employers were paragons we wouldn't need unions. But they're not, so we do.
As an employer I'd like to think that anyone working for me is free to join a trades union - but nevertheless I know I'd be mightily pissed off if staff walked out because their union had instructed them to do so in sympathy over a totally unrelated dispute with another employer.
That was one of the bad things about the unions in the UK in the Seventies. Unfortunately the outcome was one of those classic medical situations when Thatcher set out to "reform" industrial relations - "The operation was a complete success, but the patient died." Slowly, tentatively, trades unionism in the UK is coming back out of the shelters and ceasing to be a dirty word, and that's a good thing.