Employers, I'm begging you, please stop firing union organizers. It's illegal. It's also a terrible union avoidance strategy because you're playing right into their hands.
1/ It's illegal retaliation
Section 8(a)(1) of the National Labor Relation Act makes it illegal to interfere with, restrain, or coerce employees because they exercise their right to form, join, or assist a labor union.
Section 8(a)(3) makes it illegal to discriminate or retaliate against an employee as a means to discourage membership in a union.
You violate both when you terminate union organizer or other pro-union employee because of their organizing activity.
2/ You're not helping your cause
Amazon fired Chris Smalls and it got them organized. Starbucks has fired too many union organizers and cut the hours of others, and it hasn’t slowed or stopped their efforts, either.
Do you really think a termination will stop them from talking to your remaining employees? All it's doing is stopping them from talking in person while working. But they still have email, text messages, Facebook, Instagram, Twitter, SnapChat, and TikTok, not to mention in person meetings outside of work.
Moreover, firing a union organizer plays right into the hands of the union. It creates a martyr to inspire your remaining employees by demonstrating why they need a union in the first place.
In other words, you're accomplishing little because you can't stop most communication between the fired employee(s) and your remaining employees, while you're simultaneously helping the union prove its point to those remaining employees.
Don't fire; engage. Tell all employees why you are an employer of choice for them without a union and what will (and won't) change with a union. Enlist the help of employees to advocate on your behalf with their coworkers both as to why you’re a quality employer and why they should vote union "no."
If you can't make that compelling argument and find allies to enlist in your cause, then you have deeper issues that go well beyond a union organizing campaign.