>You've somehow managed to bring two logical fallacies in the same sentence — the straw man and the false dichotomy.
You're misreading.
I presented two possibilities, but nowhere did I claim that they were the only two possibilities -- ergo, no false dichotomy. You aren't clear about where exactly you believe that I presented a straw man, so I can't respond to that one. If you're saying that modern union shops do not result in the sort of inefficiencies I mention above, then the kindest response I can find is that we must have very different experience of union shops. I invite you to examine the union-imposed rules at, e.g., Yale Medical School, which is what I was particularly thinking of when I wrote that.
> The purpose of unions has always been to bargain collectively in situations where individual actions alone would result in a greater detriment to each worker.
Thank you for that basic restatement of the definition of "union." You did, however, leave out the important bit: that the nature of union bargaining is always the workers of a corporation demanding policy changes from the owners of a corporation.[1] These changes always involve a cost which reduces the bottom line profit of the corporation -- e.g. higher pay, shorter hours, etc. From a strictly short-term, monetary POV, anything that reduces the bottom line is non-optimal. In the long term, however, or when other measuring sticks are used (social health, GDP, etc) these changes may be enormously better than the policies they replace, because they result in more total wealth in the hands of the consumer, more leisure time in which to consume / innovate / create / be healthy / etc.
This is exactly what I said in my original post. Hopefully you will more clearly understand the more spelled-out version.
> A corporation is by nature this same mechanism [for using collective action when individual action would be sub-optimal] applied in the market, so which side you prefer — the worker or the owner — is fundamentally one of politics in the end.
While this is technically true (as in, it does not contain an explicit inaccuracy), there are some significant differences between a corporation and a union. Most notably, the benefits of being in a union accrue essentially equally to all members, whereas the benefits of being in a corporation do not -- the owners and top officers reap far more of the rewards than the "bottom rung" employees. Furthermore, their incentive structures are very different -- a tech support guy is paid $N/year as long as he shows up for work and the company doesn't go bust (incentive to keep the status quo), but the CEO is making most of his money off of stock options and/or bonus (incentive to change the status quo).
[1] I'm using the word "corporation" loosely here because it's more commonly applicable and it's easier than naming the various possible employing bodies (government, NGO, non-profit, etc). Most often it's a corporation per se.