Hammer him mercilessly on this. Do not let up. Do not get self-embarassed into thinking you are being overly repetitive. He has told you it got to him. Get to him more. And more. He has invented his own bumper sticker of doom. Stick it to him. He will own it.
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When we were in grade school, I remember being angry and calling my big brother the worst name I could think of: “Buddy Belly-Button”. It got to him so I used it plenty of times just to tease him.
Of course, we were children then.
Relevance to the OP is slight, I just felt like smiling a bit.