the one you imply with your question, namely that liberals tend to assume that black people are less able to handle rudimentary, customary responsibilities, like obtaining IDs. The underlying assumption, when you get past the rhetoric, is precisely that: black people won't be able to navigate the procedures necessary to obtain identification.
Did you happen to see any articles on a recent study done about language and political beliefs? The researchers found that while moderates and conservatives generally speak the same to members of minority groups the same way they speak to whites, liberals tend to adjust their language "down" when speaking to them. You've probably experienced this before. I certainly have. Many times. The ones that stand out were examples in college. Occasions in which black students misstated facts, mispronounced words, or made points that were obvious and added nothing to the discussion, which then were left uncorrected or were not constructively criticized . Now, it might be explained that the professor and the other students did not speak up out of fear of being labeled "prejudiced," but I don't think that fully explains it. There is an underlying, paternalistic belief that members of minority groups can't be expected to do the same things as most whites can do. Like using proper terminology or diction. Like find the DMV or figure out a way to get there when they're poor. Unsurprisingly, these ideas seem to be much more prevalent among people in the intelligentsia and higher socioecnomic strata, rather than among working class whites. It turns out that assuming a belief system that you believe is most compassionate towards black people doesn't produce a great affinity with actual black people, nor does it provide you with a better understanding of their lives.