This could be a deliberately strange use of vociferous, but it is certainly strange. A person is, or is not, vociferous depending entirely on how they behave. A person is, or is not, popular depending on the opinions of other people.
Of course, this is an arty/cultural context. Vociferously popular could well mean that not only is this person popular, but also that his supporters are vociferous in their support.
Still, I don't like it. I suppose an equivalent twisted pair of words would be arrogantly admired.