What should I do with my dog?

My dog Rufus is a Weimaraner. Myself and my partner got him 8 years ago and chose him forhis docile temperament. Since then he has given me and Graham many years of enjoyment and companionship. However yesterday when Graham scalded him for straining on the leash he lashed out and savaged Graham's hand. Graham is insistent that Rufus has to be put down citing that he has 'had a good innings'. I can't bare to part with Rufus. What should I do?