What to say…

He enjoyed being mean. I saw his gloating smirk as soon as I entered the bank.
He leaned toward the teller and snarled, “Why are you counting everything again? Do you think I’m trying to cheat you? Jeez, really. Cut me a break.”
She was only doing her job but her fingers stuttered, nervous under his scrutiny. She was young, maybe twenty-three. Small, too. Probably half the size of the man who scoffed at her. Despite his boorish behavior, she couldn’t walk away. He was a customer. She had to treat him well.
That’s the type of situation every bully loves.
“I don’t have all day,” he muttered, turning his head and rolling his eyes so the two people in line could see how unhappy he was to wait.
The woman beside me looked away. She knew he wanted an audience and she wasn’t going to give him one.
I probably should’ve looked away, too, but that gloating smirk of his was too much for me. I wanted to slap it off his face. He was an older man, old enough to be a grandfather, old enough to know that he could choose how he reacted in this situation. He could’ve been kind, but he chose to be cruel.
I glared at him for a long moment and then looked at the wall as though the beige paint was much more interesting than he was.
The bank teller finished the transaction and handed a receipt to him. At this point, I was trying to figure out of I should say something. I really wanted to, but I knew that if I angered him, he might wait outside for me. Things might escalate. So, I decided to swallow my words, but I’m sure my expression said it all. I thought he was a total jerk.
On his way out, he paused next to me and murmured, “Don’t fluster her. She panics.”
Anger pulsed out of me in waves, but I completely ignored him. I acted like he didn’t matter, that his words weren’t worth a reaction. Inside, though, I froze. I wanted to say something, but no words came.
He sauntered away, the self-appointed King of How To Conduct a Bank Transaction.
Ten seconds later, I knew what I should’ve said: “She’s not the problem.” That would’ve been a good response. I wanted to defend her, but failed. I’d failed so badly, the bully decided to speak to me on his way out of the bank.
Later, when I told my husband this story, he shook his head. “No, Lynn, that guy knew you thought he was a jerk. He was trying to convince you that the teller made him act that way. Even though you didn’t say a thing, you got through to him.”
I felt a lot better after hearing that, but I still feel like I didn’t do enough. What is the best way to react in a situation like that?