I've honestly never heard anyone celebrate white people wearing dreadlocks without being immediately dragged through the mud. Nor have I heard people who think dreads are filthy conveniently make exceptions for white people. Is this actually a thing that happens?
I've never seen it. Everybody I've heard complaining about filthy dreads almost exclusively says it about white people with dreads, regardless of their position on whether or not dreads are cultural appropriation. I have never actually witnessed anybody saying that about black dreads even once in my life.