Do you really think the people offended by this tweet would have been less offended if Bing had originally tweeted that the donation was already made? I doubt it, especially considering that their follow-up tweet which did just that has only further offended those who have chosen to be offended.

I think the idea was for the $1 donation to be an incentive for people to retweet, which would spread the link to the Microsoft Disaster Response page.