The Captain has the responsibility to ensure the safety of the flight. If an individual undermines that authority by publicly mocking that authority the Captain is fully justified in going to the next step of “what if” an in-flight emergency develops. Is this individual going to obey the crew commands in an emergency? Or, as this individual has already demonstrated, flout authority?
It appears to me that this individual showed an amazing lack of good manners and judgment with zero accountability. Hmm it’s almost akin to the behavior of a child yelling for his “Mommy” because someone has shown him that this type of behavior is unacceptable and will not be tolerated.
This incident is all about safety and if the Captain had not removed the offending party he would have been remiss in his duties