First, the amount of racism among members of the republican party is not relevant. We do not have to be lilly white in order to assess democratic racism. Racism in the democratic party is not excused by the existence of any racism anywhere else.
Also, we can accuse the democratic *party* of being racist, and institutionalizing racist practices without accusing *all* democrat *voters* of each being racist.
I would argue that is the case. It is unwritten (and written) policy to use race to further party goals. It is party policy to forment racial disharmoney. It is party policy to treat black Americans as second rate citizens while accusing republicans of conspiracies and plots to sicken and kill black Americans.
Exhibit A might be the rigid racial, ethnic, and gender quota systems that Democrats have maintained for selecting delegates to their national convention ever since the McGovern convention in 1972. Since there is hardly a more important function for a national party than choosing (and supporting) a presidential candidate by these delegates, this is very strong evidence of the Democrats' internal thinking on racial, ethnic, and gender matters. And their general support for racial quotas throughout American society would be Exhibit B.