You get fired, and you think it was because of something you said on the job. As such, you instantly think it's a wrongful termination. After all, doesn't the First Amendment to the Constitution give you the right to free speech, automatically protecting you from being fired for what you say?
This is a common myth, but that's not actually what the First Amendment does. As unfair as it may seem, free speech does not extend into the business world.
Free speech is a protection against the government itself. Essentially, it means you can't be jailed for what you say, and the government can't set up laws instructing you to say only certain things. It was established so that a tyrannical government couldn't take over and then jail anyone who spoke out against them.
Your boss is not bound by the same rules. You can be terminated for what you say on the job. If it's controversial, for example, they may fire you because what you said casts the company's image in a negative light and impacts its success.
Another way to look at this is that you do have free speech at work. You're not going to be jailed for speaking your mind. However, that doesn't mean that you're free from all of the consequences of what you say, and one of those consequences is that you could lose your job.
As you can see, this common misconception shows why it's so important for American workers to know what rights they have, both inside and outside of the workplace.
Source: Huffington Post, "Can You Be Fired For Your Political Beliefs Or Activities? Maybe," Donna Ballman, accessed Feb. 16, 2017