They have no right to do this, they are simply security and nothing more.

They may prevent you from taking it through security for whatever reason they decide to make up on the day about it being liquid/not clear container/wrong size/not dense liquid/not in a sealed bag but they cannoy cannot forcibly take items away from you against your will. They can prevent you passing with any item they decide they don't like but cannot just take it off you.

Despite what they think they are not above the law and it's about time some of them got a reality check. I mean the idea a 2.5cm pair of scissors could be banned from an aircraft is ludicrous. They seem to slowly be progressing to TSA style where they think they are "defending" the skies.