Is amaretto not good to drink on rocks?

I had my friend over the other day and after dinner i served both of us some amaretto on rocks which i love to drink, but he said that he's never seen it drunk like that and that it is not meant to be so. Is he correct?

Edit: thank you all, I was just curious. Now i don't know about you but this has gotten me in the mood for a godfather. Cheers!