I too can't get a read on if he's just an old-fashioned grampa whose pish-poshing our crunchy ways and just going ahead with his favorite way of bugging the little ones, or if it IS sinister. Something to think about is this, tho... Baby-boomers, and THEIR parents were VERY often the products of SEVERE physical and sexual abuse. It was the NORM. This leads SOME folks from those generations that came before to have pretty callous views of children as ENTITIES, other PEOPLE with preferences of their own. Grampa was picked on, by parents, siblings, peers, and sh*t rolls down hill to the youngest generations.
Inside, whether we're 10 or 90, we're all still products of what happened to us and how it was dealt with. Grampa might just need a frim reminder in THAT moment. My mom does, sometimes. She does the same tickly-grabbem-up stuff she did with me when I was little, and sometimes she goes a LITTLE too far, and I can see in Prenna's face that she's NOT down with it. She is an outspoken girl and will say NO NANA! But still my mom persists sometimes. That is where I say, "Nana, I hear Prenna's words, she said NO." This is EMBARASSING for my mom, but effective. It is the same verbage I use whan Prenna acts out against another child, So-&-So said, no, Prenna, I hear her words.
IF HE STILL PERSISTS, he's either stubborn, dumb, or rude, and that requires more private handling. A conversation between your 2 "camps"... Good luck, sista.