In defense of complex financial derivatives

I wonder if that article has been written by a Markov Chain.

He's right. Derivatives are nothing but mathematical relationships between other things. If those other things have prices, then the derivative has a price in relation to them.

Derivatives are useful when you want to design an instrument with specific risk/return characteristics.

In the case of the derivatives that everyone is blaming for the financial crisis, they were considered low risk. But only because everyone thought that housing prices would not dip more than a few percent.

There is nothing "riskier" about such a derivative than there is about someone buying a house, also thinking that housing prices wouldn't dip more than a few percent, yet nobody is suggesting that home purchases be banned.

There is also the issue of flawed ratings given by Moody's, which resulted in derivatives whose risks were not accurately calculated and thus not accurately priced.

It might be a defense of complex financial derivatives if you're willing to work through the jargon, but otherwise it just looks like a bunch of technical blah blah being thrown around without much in the way of actual "defense of complex financial derivatives". Either he's aiming for the few who understand what he's saying (which seems odd - presumably they're able to form their own opinions, due to their knowledge of it), or he's unable/unwilling to put together a pursuasive argument in English, which makes it sort of a waste of time.