HN is not the best platform to from anti-capitalism sentiments. There's a lot of privilege here and it makes people pretty blind to how awful capitalism is (and the things it creates, like anti-union sentiment).
Unions deal in money and don't seek to change that, unions recognize and don't challenge ownership of the business.
What about them makes them anti-capitalist, except that they seek to shift the balance of "who, of all the people working on a business, gets paid what for the operation of a business"?
I knew someone through a friend that was kicked out of the carpenters union for not being good enough. Their accreditation can be quite strict.
They only exist because without them, capitalism and its advocates brutally oppress the workers, keeping them in a perpetual state of poverty. The fact that they are not literally trying to overthrow the regime doesn't mean they aren't anti-capitalist.
Amusingly, this hypocrisy is literally embedded in US antitrust law: https://www.law.cornell.edu/uscode/text/15/17 Literally "price fixing cartels are bad, except when they aren't".
Which they did, everywhere they were implemented.
It took years of fixing the system with child labour laws, union laws, anti-discrimination laws, factory strikes, workers riots, civil rights laws, minimum wage, etc.
Capitalism works in the Nations where it does because of years of regulation to make it more fair and to weed out exploitation.
People wanting to dismantle the state right now (and make no mistake, many of these riots have a lot of anarco-anti-cap/antifa people in them causing the violence) do not understand they will not get a better State. They'll be lucky to get some stable regions, but when a State falls there's a power vacuum. Then you have to start over .. and there will be a ton of corruption until you get everything "right" again.
Actually it's because of years of union-organising, putting pressure on companies and governments to implement these measures. Without unions, we would have none of these improved work conditions and protections.
I wonder how people could make such an argument if they have historical records of business owners rejecting more paying customers and spending more to put together duplicate infrastructure just because they felt that some paying customers had to be subjected to degraded levels of service just because.