On throwing pillows from the sofa

Two days ago I went to the "official" birthday cake-and-coffee for my smaller little brother, who turned 19. My cousin's family with their 3-year-old son were there. He was very interested in the room that is full of (mostly my) old junk and overall being a happy curious child. 

What made me think was how he enjoyed throwing pillows from an old sofa. My brother tried to stop him, and to talk him into 'cleaning up' after himself, making him promise to put the pillows back on the sofa after he was done with them. It didn't work, and I didn't support my brother but I engaged with the boy's play, throwing the pillows back to him, laughing along with him. 

Later when the boy tried to go and throw some more pillows, his father stopped him, saying "no" and tearing him away. I'm left to wonder what harm he could've possibly done - mostly probably to the ego of the father who was maybe concerned with what we would think about his parenting skills? 

This is a perfect example of a situation in which just saying yes creates the space for joy. Maybe the father could have asked us if the pillows were valuable, or if there would be something less valuable to throw around? But he obviously didn't consider the experience and joy from throwing pillows valuable or "something to indulge".