Calling Bitcoin a pyramid scheme is a very ridiculous assumption, i bet whoever write that article has no knowledge about finance. I really love the points you gave in debunking the claim.

I don't know what people stand to gain in tarnishing the image of Bitcoin. Anyway there have been a lot of attempts in the past do i am not surprised. Ponzi schemes have pyramid structure, Bitcoin don't, rather Bitcoin is structured just like our regular Dollar and Pounds, the only difference is Bitcoin is decentralized which makes it even better.

 So if Bitcoin is a pyramid scheme, Dollar is also a pyramid.