Pedal and Cassette Shake I really need your suggestions.
The situation is bellow: I have bought brand new one "Specialized Rockhopper Sport 29" 2017 satin navy-hyper" in a official dealer of Specialized.

When i arrived at home, just for interest rotated bicycle and checked the spinning... during the spinning i noticed that pedal and cassette was shaking - confused, went back to shop and asked them for change but they told me that this is totally normal and there is no bicycle without this.

Maybe it is a hub problem and thats why it shakes.

Still wondering, need your advice, should i take care about it or it is normal?

Here is the video:

Youtube: 
                
            

Vimeo: https://vimeo.com/236250012

Please consider the fact, even when i touch to cassette it is obvious that it shaking really.

Thanks a lot. 
Look forward to hearing from you people.
I can't see anything wrong at all.

The any vibration you may feel when the rear wheels is spinning but the cranks and chain and cassette are not moving is due to the clicking of the pawls in the free-hub.

I think if you hold a pedal and spin the cranks so the rear wheel turns you will not detect any vibration or 'shaking', as the free-hub will engage.

I think if you ride the bike you will find it functions normally.