That joke isn’t funny anymore

So I was browsing at the hardware store because (oddly enough) this particular hardware store has a decent selection of bakeware and other bits for the kitchen. While I was smell-testing the various scented candles on display (at the hardware store) I noticed an old man staring at me from behind a display of discounted Christmas decorations. I stared back, something I don’t normally do. Usually when I catch people staring at me I turn and flee. But this guy was ancient and I don’t fear old people.
He saw me looking at him and took that as an opening. “What are you?” he asked in a heavy tagalog (Filipino) accent.
“What am I?” I asked back. Normally I try not to answer a question with a question, but I didn’t have my hearing aid in and thought maybe I had misunderstood him.
“Yeah, what are you? What’s your nationality?”
“Oh! I’m Chamorro and Filipino, and the rumor is one of my great-grandfathers was an Irish man.”
It takes a second to process. He leans over the counter. “So you’re Filipino?” he asks, like he needs confirmation.
“Yeah, why? Are you going to give me a discount?” I ask, giving way to sarcasm.
“But you’re just half?” he presses.
“That’s right, just the top half. Does that mean I only get 10 percent?” I’m on a roll.
He obviously doesn’t get my sense of humor. “So you’re a mix breed.”
“What, you mean like a dog?”
He laughs like it’s the FUNNIEST THING.
“Looks like you could use some manners,” I say.
“What’s that?”
“I said, LOOSE NAILS and HAMMERS.”
“That’s aisle 5, at the back,” he says, pointing in the direction. “Come back here when you’re going to pay, I’ll give you a discount.”