Sure. How about voicing the controversial opinion that private citizens should have a right to free speech without being fired (as in, believing that free speech should apply to more than just the government).
IE, free speech, applied to private companies, as the controversial opinion that a person is getting fired for.
A company has to continue to employ you no matter what dumb things you say at work?
(Also, no place worth working for will fire you for saying “private citizens should have the right to free speech without being fired.” What is the controversial opinion you’re actually worried about expressing at work? That Windows Mobile is making a huge comeback? That pina colada Oreos are tasty?)
Apparently, free speech is so controversial, that people like you believe that a person who supports free speech must obviously hold some sort of deep dark evil opinion.
The fact that you automatically assume some nefarious motive, proves that supporting free speech is indeed a controversial opinion to hold, and that it is rational to be worried about being persecuted for believing in it.
