I've worked for Walmart several different times throughout my life. Two stores in different areas and a grocery warehouse. Watching, reading and listening to Anti-Union propaganda always took up about 30% of the new hire process. I've also heard stories of Walmart closing down stores and completely pulling out of areas where the unionizing process got dangerously (for them) close to finalizing.

So yeah, an international company firing a dude just for talking about unionizing doesn't fucking surprise me in the least.