Every time someone says, “Don't get me wrong, I'm not racist but...” I just look at them and say, “... says every racist just before they're going to make a racist comment”.
When my brother made a racist generalisation, I said “I'll just go & get your white hood & cloak for you then, shall I?” He was silent then & I could see he was thinking it over.
A newly married into the family member used comments such as Abo, coon within her conversation, which she didn't think twice about as being in the category of racist behaviour. On the second occasion hearing it I informed her sternly that those words are racist and if she could kindly refrain from using them in our family home. She got the point, however, sadly would make the comments in her own house. So I made excuses to not to attend events at her house even to the extent of ensuring the events where mainly at my home to prevent her racist behaviour. You have to pick your battles wisely as ignorance can be part of a person's nature and battling them everywhere can be a waste of energy...I happy with my own little win :)