Frankly, none of the reasons you give really matter to me more than the justification that you have the right to bargain with your employer through your union. Should you and your fellow union members feel the need, you have the right to strike.
When are people going to wake up and see that unions rose hand in hand with prosperity of the middle class, and as union membership falls, with it falls the middle class. The destruction of unions in the USA (with Canada’s unions following) is not just happenstance, it’s the result of a concerted effort by business and right wing governments. Anyone who is paying attention should be able to see that all the workplace rights we used to have are being eroded. Pay is going down or staying flat, benefits are disappearing.
We are told that the free market will set fair wages and working conditions, but the free market isn’t actually free, it’s rigged in favour of business. Employers in many states can fire you for almost any reason, including because your sick child is driving up health insurance costs. Or because you didn’t show up for the company PR photo for the local Republican politician.
Or because you voted for the wrong political party.
Republicans complain about illegal immigration, but they refuse to enact laws that punish employers who hire illegal immigrants, putting businesses and their employees that follow the law at an unfair advantage.
Even white collar workers are seeing how businesses take advantage of loopholes, and just plain cheat, bringing in educated workers from abroad on temporary visas. These are only supposed to be used when the company can’t find US workers to fill the position, but they get around that by asking for specialized skills, which the foreign worker says they have, but frequently don’t. The practise has become widespread and many companies no longer even bother with that pretext. American workers are being fired and replaced with foreign replacement workers, a clear violation of the law.
As a final kick in the teeth, the American workers frequently have to train the new workers or else they don’t get their severance pay. These white collar workers are often non unionized and don’t have the clout or financial resources to fight these illegal acts. Unions have the ability to fight both legal, lobbying and PR campaigns for the benefit of it’s members.
At the end of the day a union is just an organization that helps protect your interests at work. They are not sinister, they help ensure that income equality and work place rules are fair, and is not the complete farce it has become in many states in the USA.