bafanguy, My personal thoughts, if there are any sort of industrial issues going on between pilot and company, I would be steering clear. It's a bit ultruistic to think that a race to the bottom using pilots on Visas to shore up numbers when conditions are no where industry standard is just about numbers.
When you're a guest in a country it's up to the person to obey the law, rules, regs and perhaps just as importantly the societal norms, industry norms. If it's expected that union membership is a cultural standard, join. If the union advises certain, legal industrial action, then you follow it. You don't just go to the country, get what you want and piss off. Leave a place better than when you started and all.