Amid an unusual spotlight on IRS conduct, a Colorado businessman contends his case is one the government particularly wants to keep hidden, because it could cause the whole federal agency to self-destruct. Jeff Maehr, a Colorado chiropractor who has engaged in a number of business ventures, including PureHealthSystems.com, admits he has refused to file federal income tax returns since 2002, but he says the IRS is afraid to press criminal charges against him.