Why would families disown a love on for being in an interracial relationship?

I don’t think that’s fair at all! Most of my family has different opinions on it and most prefer their own race and tell us to stick with our own kind but as long as we’re happy it doesn’t matter. I have a few relatives that are against the idea. One of my cousins is in an interracial relationship and her parents are against it and still are. She told us her parents said if you ever bring home non white man, we’re disowning you. I think that’s pretty harsh. Their opinion didn’t matter to her and she wasn’t giving up the over of her life and he treats her so good. Very kind man. Her parents and her dads side completely disowned her and never went to her wedding or met their three beautiful grandparents. They said they don’t want half….well half black grandkids in the family. I can’t say the N word because it’s offensive to black peoples. Why do people disown others for stupid reasons? Love is love no matter what color.