It does sound like the passenger was indignant and untactful, but nowhere near an abusive level that warrants being kicked off.
And I'm with the passenger, in spirit - it's fundamentally American (the country, not the airline) to stand up for yourself when you're being picked on.
Alas, too many front line employees in this country have absolutely zero sense of subservience.
You can be yelled at for putting money on the counter instead of in the cashier's hand during a retail transaction.