black voters (and social media lurkers) have made up their own minds about Romney one way or the other based on their own experiences, access to information and other elements informing their world views. Most black people have concluded that he's not good for the country and/or not good for their interests.
Dash is well within her right to not be among that number. And people really shouldn't be foul to the woman on social media. But like anyone else who thinks Romney's a horrible choice for President, black people have a legitimate right to wonder aloud about just how Clueless the actress supporting him may be.