I'd always believed it was up to the grandparents (step or otherwise) to decide what they would be called, regardless of how difficult the situation is. On the other hand, I know too that there are emotional attachments to different titles, and it must be difficult to see someone you don't like appropriate a title so affectionate as "poppy". I'm sorry you are caught in this dilemma.

I think a compromise - your dd calling him Poppy and you calling him whatever you want (including rude words under your breath ) - might be the best solution, and taking FlowerChild's approach might be best.

On a lighter note, my dh wants to be called Pop when we are grandparents. That's what my FIL is to his grandkids. Unfortunately, it's a title that for some reason I really hate. I like Grandad or Grandpa, but not Pop. Sucks to be me, I guess (I shall be Grandma, thankyouverymuch, as long as it isn't too soon!!)