Legal and Ethical are two different things. Confounding both, in the eyes of people is Understanding.
It may be legal to something, but unethical. It may be ethical to do something, but illegal. There are many examples of both. The reason for this article is apparently to spread understanding amongst people who think it's unethical to do HFT, but may not understand what HFT does and how it works. By writing this article, he is hoping to convince - via understanding - people that HFT is also ethical.
It may be legal to something, but unethical. It may be ethical to do something, but illegal. There are many examples of both. The reason for this article is apparently to spread understanding amongst people who think it's unethical to do HFT, but may not understand what HFT does and how it works. By writing this article, he is hoping to convince - via understanding - people that HFT is also ethical.