"Pushing up wages creates unemployment by making employers less eager to hire." There's a lot of assumptions in that statement. First off, I haven't read the Activision-Blizzard article, I work in an industry adjacent to games, but I can see a scenario where it makes sense to lay off people the same year you make record profits. It just looks really bad. Just because you're making money, doesn't mean you have more work you're willing to pay people to do. Businesses aren't charities, ideally they profit by filling demand. The fill that demand with workers. Along the way they try and fill that demand with fewer workers and leveraging previous investments.

Back to the quote; unions also prevent companies from squeezing existing workers too much, forcing them to hire more people. That quote assumes the only thing unions do is force wages unreasonably high. Whether a company hires more people has more to do with demand (or investment in future potential demand) than income.

"The way to improve conditions for workers in general...is to raise worker productivity." The reason people would want some sort of collective bargaining is that they feel increases in worker productivity go disproportionately to the business owner instead of the worker because of the power differential. I'm not saying unions are the perfect answer, but every anti-union thing I read hand-waves this away as not existing or not needing to be addressed.

"In the best-case scenario, unions engineer a transfer from consumers and relatively immobile employers to themselves, with considerable deadweight cost in the process." To me this sounds like rent-seeking. I think it's disingenuous to say this is "in the best-case scenario," it's not a great outcome anywhere it happens, but unions aren't the worst offenders, by far.

Also consider the source.

They are a libertarian think-tank.