Source? I am relatively certain you are wrong. I have found nothing about tweets after the initial commercial. Here is a blog posting from the time it happened:
Now, in addition to the Cheerios YouTube post – under which comments "devolved into an endless flame war, with references to Nazis, 'troglodytes' and 'racial genocide'" according to a story in Adweek.com before they were pulled – angry viewers have migrated to new comments sections. Racists and angry commenters are continuing their diatribes under other YouTube posts as well as under the Adweek piece, a story on CBSNews.com and a New York Daily News story.
And the NY Times article about it:
None of these reference twitter, other than to mention people on the backlash to the supposed "backlash."