Grown ass men throwing a temper tantrum like children ruins my day

For context, I work at a retail pharmacy. Had this guy today to come pick up his meds. I politely asked for his name and date of birth, and he gives it to me. I asked him, again politely, to spell out his first name for me. He replies, "It's [name], like the beer company."

I, once again very politely, ask him to spell it out for me. This dude literally stares at me for a whole 5 seconds and repeats the same thing. This time, I literally told this guy that I don't drink beer so I'm unfamiliar with the company, I need him to spell his name out, both first name and last name.

For God knows what reason, this guy starts screaming at me telling me that I'm showing him attitude and tells me that I'm the most incompetent individual he has met in his entire life, and that they should fire me. He also asked me to get someone more "comepetent and diligent" than me.

I got so mad that I left and asked someone else to take over. Mind you, I've been standing there for 8 hours, putting with other people's tantrums and haven't had food or drink during those 8 hours. I really wished I could say something to this bozo's face but really can't risk getting fired.

Thanks for listening to my vent lol, had to get this off my chest.