I don't think unions are themselves a good or bad idea, its the interface with the company that can bring about a better working relationship and maybe offer other options.
Unions don't run airlines, and never will because most pilots are far too selfish - pilots almost always vote for what will benefit them rather than voting for the moral right.
Unions in airlines can work and can help relations. I worked for a major UK airline where the relationship between company and pilots had got so bad we were literally on the verge of a strike. We came back from that and these days the company and union try and work together. We recently needed to make 150 or so pilots redundant. Well, in the end all of those pilots kept their jobs. I am not saying these problems were averted only because of union recognition, but it certainly helped.
Union recognition and a successful airline are not mutually exclusive and usually it is the opposite.