Honestly - not that I could tell. I was not there with any black friends, so I'll have to get their opinions later. I'd probably say that most viewers would just forget about it when they left the theater and not give it a second thought. But right at the moment the Twins delivered the "reading" line, there was definitely some questioning reactions from certain black audience members sitting around me. Not a lot, mind you, but some.
And to the question of "Is Bay racist?", I would say probably not. He's just a clueless middle-aged Hollywood rich white man trying to reconnect with the youthful black audience he had back when he did "Bad Boys". He just took it too far and made the mistake of not balancing the Twins with some less-sterotypical character traits.