Trump needs to reassure the people that he is not going to support bigotry. There are many people in the country who are hurt that a platform based in bigotry and hate helped elect the next president of the United States. Having Steve Bannon as his advisor hurts his standing with the American public.
Even without knowing the identity of his backers, Bannon’s designs are clear enough. While he’d blanch at the comparison, he’s pursuing something like the old Marxist dialectical concept of “heightening the contradictions,” only rather than foment revolution among the proletariat, he’s trying to disillusion Clinton’s and Bush’s natural base of support, recognizing, as Goldman Sachs taught him, that you’re more effective if others lead the way.
Yes, Bannon's experience at Brietbart absolutely hampers his ability to advise Trump. Most of the "non-established" members of his team have so little experience in government and Bannon comes from a radical place of complete bias and no compromise. He isn't going to help build consensus and many Washington insiders are very wary of him.
Steve Bannon ran Breitbart News, an extreme Alt-Right publication, but Donald Trump has shown himself in sympathy with many of their ideas, so his choice of Bannon as advisor is sensible. Luckily Mr Trump will have other advisers, like Reinz Priebus, who will be able to give a more balanced view to Mr Trump. The two will complement each other.