Absolutely false!
You can be fired for engaging in lawful activity in your personal life outside of work hours... whoever told you that lie, doesn't know what they are talking about.
On what basis?
I've had occasion to demonstrate this exact condition, on three separate occasions, to former employers by having had assorted courts tell them first-hand, and in so many words, to either revise this curious and unlawful viewpoint, or else pay rather exceptional amounts of civil damages.
If you ACCEPT, as presumably a condition of employment AT THE TIME you accept employment, the condition that your employer may in some/any fashion regulate your non-business, off-time, and otherwise lawful activities, well, fine. That's up to you. No quarrel here.
When, however, AFTER having been employed, the employer makes such an attempt without your consent, he/she/it is in DEEP weeds at civil law.
Consult your attorney; you'll find out immediately that I've told you nothing but simple and easily demonstrable fact.
FReegards!
Please show a link/law that says this. I know 2 homosexuals who were fired for kissing in a mall and were fired by their boss who witnessed it. they won the law suit - damages were not disclosed. So where do you get your information.