I always thought the idea of the guy getting sent out with his little camcorder when some of the more controversial songs started getting sung was so they could catch them on film, identify them later then go knocking on their door at 5am.
For what it is worth I couldn't give a damn what other sets of fans sing at matches and to be honest I don't like the tit-for-tat fake outrage that seems to follow the game about these days. Saying that though, if the plod do insist on using all these tactics they should at least be following it up with a few arrests.