[Broken_Hippo]

Yes, but in most cases we are arresting people for planning a crime, not just nonchalantly discussing it. Handing out recruitment flyers for an organisation that bombs others? Planning to murder your wife? Planning on defrauding x out of their life savings? You know, actual plans that meet the burden of proof for a criminal investigation. Yes. Please prevent this stuff that folks are planning.

[dzdt]

Only more often it is the police who pretend to plan a crime and recruit suspects to participate in that fiction. If the suspects show willingness to participate they get arrested.

[1]http://www.npr.org/2014/07/18/332636882/newburgh-sting-terro...

[2]http://www.seattletimes.com/seattle-news/was-fbi-grooming-po...