Why does Fred, despite Scrooge's rudeness to him, invite his uncle to Christmas dinner?

Fred doesn't give up on Scrooge despite all of his rudeness towards everyone else

Fred is hoping that his uncle will finally accept his invitation to join him at his home with his wife and friends for Christmas dinner. Fred does not give up on his uncle, as is evidenced by the fact that he is a grown man and still trying to have a relationship with him