Just as long as they aren't secretly worshiping the corpse emperor they should be ok. Too many chaos worshippers get hung up on impurity tests and being "the right kind of chaos" when we really need to be presenting a united front against the followers of the corpse emperor. Chaos unity is important, we all want a galaxy free of the imperium for the glory of our dark gods, and if we spend all our time arguing amongst ourselves that can only serve the corpse on terra

Chaos Undivided Thought is the best path forward, and you don't want to fall to revisionists that say Abbadon should have focused on building Chaos in the Eye of Terror before spreading it to the rest of the galaxy, but you shouldn't disregard those sympathetic to our cause just because they are more dedicated to perfecting their murder-symphony than they are spreading Papa Nurgle's gifts