The mistake here is ASSUMING it's "liberals".
It could simply be citizens of New Orleans who are pissed at Republicans for how they left the city AFTER Katrina.
Worse, the Republicans NEVER ONCE mentioned Katrina and the shitty cleanup job they did there during the entire conference. We know why. Republicans have only contempt for the poor and the middle class. They are always trying to figure out new and exciting ways to make the lives of poor people even more miserable.
Some think the Republicans failed, but we know they didn't. They screwed the people of New Orleans and that has always been part of their weird plan.