So if I could only detect this one prank site, but did not have a way to detect and downrank all prank sites at once, you would say it's invalid for me to just take action against the one I know about, since that's not a universal solution?
Well that depends. If my position were that you have to act via "web-wide decisions" and "universal solutions", then I might conclude that my only options were to leave up all prank sites, including those damaging the usefulness of my search results, or remove everything including harmless parody accounts.
On the other hand, if I were to accept that it's valid to target individual sites or subsets of sites only as they become a problem, then I might conclude that removing this one troublesome prank site that is pointing my users to bad information does not require me to take action against random twitter parody accounts.
I guess the point is that you were able to conclude that in the first place. You concluded there are options. An algorithm/decision removing one side of it means you do not, more so if you do not even get to understand why that choice was removed when you're making that choice.
