title of grandpa and grandma

Do you all think that the title of grandma and grandpa should be earned? I ask because my god awful mil is married to a horrible man that's always treated my hubby like dirt. Even when he's nice he's still awful, rude, crude etc...anyways my mil calls him "grandpa" i want to tell her next time that sorry he is not our little ones grandpa because that title is earned. He doesn't care or respect us so why should he be called grandpa? They're both never around anyways and when they are its for five minutes or less then they leave. So what do you all think? Should i tell her to please stop calling him grandpa or ignore it?