In the era of the “closed shop” I joined a Trade Union, even though working in industrial relations for the management team. Mine was a comparatively minor split-loyalty position as in that organisation as we also had a local “Worker Director” (a strong Trade Unionist) on the Board of the company.
It must be right that a body, and a Trade Union is the best option, should exist to represent the legitimate interests of employees. If employees have a voice then their commitment is likely to be greater; in my experience competent Union representatives can play a very positive role in employee relations, especially with large employers. Employer-employee relationships benefit from a sense of balance.
However, what I resented was not that I was obliged to join a Trade Union. What upset me was that, via a political levy, my union dues would be used to directly support the Labour Party. State ownership of the means of production (i.e. nationalisation of industries and then a tenant of Labour Party policy) was dubious at the time and has largely been discredited since.
Anyone should be free to join a Trade Union without any sort of obligation to support a particular political party. The purists would argue that individual members can opt out of the political levy now (thanks to Margaret Thatcher); but that option can be concealed and there can even be subtle pressures to just let the opportunity go.
Ed Milliband wants the political levy to be opt-in and that is part of the conflict between him and Len McCluskey of Unite.
What the Unite Union has to ask itself is how many more employees would join their Union if those employees did not need, by default, to support the Labour Party.