You have 6 kids so your respectivly older than 21 and have a bit more brain.. and are a bit mature,, here is what I would do
But than of course you could also do what every other looney toon just told you.
First talk to your daughter, she is 3 so she propably doesn't understand half of it. Explain her that in the 1950's when pop pop was growing up it was common to call people of brown skin niger - nigra - negro - ****** - etc.. That he still loves her and that he was propably mad about something. That some african american's will call each other ****** as a act of brother hood, but when a white person calls an african american that word its bad. Tell her that you will ask Grandpa why he said that
And leave it at that - Within 2 short hours your kid will forget it ever happend.
Than call your father in law - calmly -
Tell him - Dad, we need to talk in person - Don't do it over the phone.
When you get together with him, ask him why he said it, tell him you had to sit down and explain her the history of the word ****** and that you and his daughter are hurt by the fact he would call his grand daughter a ******.
Let him explain it. Always keep in mind that you have 6 kids, you have one grandpa. He might not be perfect, he might grew up in a different time and it might slipped out by accident. It's not an excuse, but going on the board and screaming about it is no answer.
We are not living your life, you only can. You have to deal with him every day, so you need to be mature enough to talk to him calmly.
Thats what I would do, however I am quite a bit older and I also have 6 kids, so my patience is a lot bigger than other peoples and a lot more forgiving when it comes to certain things
