Sir, in what way would your proposed filter have assisted in catching this person? Man charged with grooming child for sex.
According to the report, this person believed he was grooming a 15 year old girl for sex via an Internet chat room. Unfortunately for this particular perpetrator, the girl was in fact a police person masquerading as a potential victim.
There is NOTHING the filter could do to assist in detecting and apprehending such people. In fact money spent on such a filter will reduce the ability of real police to do real police work. After all, the money has to come from somewhere; why not a related activity.
Sir, would you please stop this insanity and abandon your filter proposal.