If a Jihadist group advocated on their website tactics to defeat security measures to detect arms and explosives, few would disagree that any responsible society should suppress it. When a website representing violent offenders, as 'Fitwatch' did, advocates avoiding detection and defeating forensics by hair dye, false whiskers and a change of clothing, clearing phone memories and the like, it is also right that a responsible society should suppress it. Likewise websites advising kiddie fiddlers how to avoid detection, or advising Nigerians how to defraud banks.
I have no problem closing down genuinely criminally inclined websites. I have huge issues with who should be able to do it - to which the answer is, not the police.
The police may by all means take their evidence before a High Court Judge, who should be able to issue an appellable interim order suspending the website. If the police are wrong, as they frequently are, those damaged can bring their evidence to open court and seek restitution. A police detective inspector is a form of life little higher than a parking warden, and not one often gifted with balanced powers of judgement, particularly in the area of free speech and free expression. Such junior office-holders should never, ever, be entrusted with such draconian powers.