Hey Cory, I'm picking nits.
Tax evasion is illegal -- tax avoidance is legal, although people debate the ethics. You used one phrase in the title, and the other in the post.
I don't think anyone would have a libel case here, since you're not saying that anyone in particular is evading taxes, but it does come across to my eyes as more of a statement of fact ("these are tax-evasion structures") than of opinion ("these assholes are way beyond the limits of ethical tax avoidance!"). That might lead people to misunderstand what you are reporting.