It really seems like you do mean to make this political. GP was talking about accusations of Tesla doing something illegal. You came in and brought up political parties and the value of unions, making the discussion much more political.

To answer your question, obviously there are both pros and cons to unions (as with basically all political issues). If unionization costs jobs, and the left considers unionization a victory, it must mean that they value the other benefits gained from unionization (e.g. improved working conditions) more than the jobs lost from it.

Perhaps jobs are not the end. Perhaps prosperity is the end, and jobs are occasionally the means to it.

If we lost half of all jobs, but a family could be supported comfortably by a single-breadwinner, would you consider that a net loss, or a net gain?

Or, alternatively, if we had 100% employment, yet all lived in poverty, would that be a better world?

Consider that the Soviet Union had 100% employment. Is that the high water mark for economic success? Why not? Inefficiency is one answer to it. Another was 'Where did the wealth surplus go?' There are others.