I'm missing my right hand, on my first visit to the US since 1994 (as a child) I was asked to scan my hand. I politely tried to tell the agent that I'd have to

I'm missing my right hand, on my first visit to the US since 1994 (as a child) I was asked to scan my hand. I politely tried to tell the agent that I'd have to scan my left hand and he started shouting at me without looking at me. Each time I uttered anything he'd just randomly shout for me to comply, after about the fourth time he looked up and ordered me to use my left hand. Absolutely bizarre experience.