Earlier quoted context omitted.
Why would any sane person be against unions? Because they, like any other organization, tend to become corrupt and exercise their power to the benefit of the "party insiders", at the expense of the everyday member. And I, for one, don't feel any need to have my pay rate negotiated based on some group average or least common denominator. And union dues. I personally fully support the right of people to bargain collect…
The problem with your point of view is that it applies equally to the companies that hire you, and they have very little incentive to be on your side.
And while the company may not be "on your side", companies are still bound by market forces, on both sides of the equation. You can't compete (for now!) without people, and if you constantly run your best people off by mistreating them, you aren't going to be very successful in the long run.