Ake said, "Politicians don't say things "innocently."

Sure they do. Maybe not when they're totally scripted (as in the convention speeches). But when even parts of their talk to an interviewer or in a town hall or stump speech are spontaneous -- as is usually the case -- they may choose their words not just innocently but often clumsily as well. Everyone makes gaffes, including politicians.   That said, I don't think this was a gaffe.
I don't think the Democrats should have to abandon this perfect, very familiar metaphor just because the Republican VP nominee had used the word "lipstick" in her convention speech.