Key, who is more well-known than Clark, could have ignored the tweet, but he made the right decision in addressing his error. Part of being an ally is acknowledging when you're wrong, even if it's difficult. An even bigger part is how you take those learned lessons and apply them in the future. Hopefully, Key won't be deterred from praising others' work in the future — after all, who doesn't want to be promoted by someone they admire? — but will instead be more conscious of honouring their efforts and originality.