"If you have nothing to hide, then you have nothing to fear" isn't a reasonable position to hold, and your statement basically amounts to it. There's plenty of reasons to want to stay anonymous when talking about business such as this.
To clarify, I don't necessarily agree with his position, but I disagree with your proposition that he is using a pseudonym for that reason.
If such a scheme were the only thing allowing you to make a profit, would you appreciate this guy drawing attention to it? In fact, you could protect your operation by submitting numerous tips to tax agencies across the world, causing his business to fail due to the immense cost of litigating such complex cases, even though he would be cleared if he could afford the defense. Everyone gets the right message: the public hears that tax havens "don't work", whistleblowers learn to keep quiet, regulators notch up another win, and the truly powerful get to continue dodging taxes.
To clarify, I don't necessarily agree with his position, but I disagree with your proposition that he is using a pseudonym for that reason.