Just because it is commonplace, it doesn't make it right.
UK police are generally quite friendly and won't use force unless it is completely necessary. I was once picked up with a friend at 2am walking home from a party. He must have known we were carrying weed because there is no way he couldn't smell it. I was also carrying acid, which made me freak out because it is a class A drug and I might have received more than a caution. He just dropped us off at home.
It isn't right to lay hands on a law enforcement officer. They are keyed up and well aware of the hatred most of the public has for them. They don't know if she had a weapon. Where the fuck are their guns and tazers and mace??? Here in the states he would be lucky if he got tazed.
Armed response only deals with armed people/bomb threats. Police will use tasers, but it is frowned upon by the public because shit like this always seems to happen.
If someone is causing shit in a public area in London you will be taken down immediately. Met police don't fuck around.
I don't know how it is in your country you touch a cop and they will beat the shit out of you and you will deserve it. It does not matter the age don't fucking touch a cop unless you want to be met with extreme force. This guy I knew wouldn't open his door on a domestic dispute call so they kicked it down and broke his jaw and three ribs. No charges stuck against the cop because he was resisting they said.