Think Dave was referring to Chaloupa's description of what the tang police are. She was rather polite - the whole concept of tang police came about because there is a school of thought that no tank is large enough for a tang, and people will jump all over someone else for even having a tang in the first place - thus, "tang police". And it's a bit silly because it seems that it's only tangs that receive this fervor of opinion - ie., angels, butterflies, etc - you don't hear of the "angel police" or the "anthias police".
Dave's just saying that anyone who feels a tang is being served an injustice by being kept in a tank, and applies those comments towards someone in a 600g tank hasn't probably actually seen this tank in person.
My guess anyhow.
Sorry if I'm putting words in anyone's mouth!