Where I live we don't have unionised/nonunionised companies you can belong to any union you want or none at all. Once you get a certain percentage of employees belonging to a single union then the company has to recognise them.
At the company I work for there are three recognised unions and obviously non-union members. For those of us in the unions the three get together with the company every year to negotiate our raises.
This year the initial offer from the company was 2.5%, non-union staff basically get told that's their raise while for the rest the union argues it out. In the end the union staff have got 6.5% plus a cash bonus (still not great but better than recent years and it comes with some changes to work-life balance and other perks to add a sweetner).
When these were announced one of my non-union coworkers was extremely upset at being fobbed off with just 2.5 and getting no bonus. I suggested maybe he join a union and then he can benefit from next year's negotiation. His response was that he'll never give his hard earned money to a bunch of socialists running the unions. I left it at that.
The next day I opened up my emails to find he'd send a department wide email. The content was going on that non-union staff were getting shafted and they shouldn't have to “pay protection money” to the socialists to get fair treatment.
He ended with a suggestion that all non-union staff should get together to negotiate with the company as a group to ensure they got fair treatment. I'm pretty sure quite a lot of people got a good laugh out of that one.