Not all conduct that impedes the lawful functions of a government agency is illegal — to be unlawful such conduct must entail fraud, deceit, or other dishonest means. Thus, it is not illegal simply to make the IRS’s job harder. Only an agreement to engage in conduct that tends to impede the IRS, and also involves fraudulent, deceitful, or dishonest means, does constitute an illegal agreement to defraud the United States.Judge Stein had variations of this theme in other portion of the Klein / defraud conspiracy instructions. For the entire set of jury instructions, see here and for the particular set of instructions on the Klein / defraud conspiracy go to pages 29-31.
For a less succinct statement of this concept see my article: John A. Townsend, Tax Obstruction Crimes: Is Making the IRS's Job Harder Enough?, 9 Hous. Bus. & Tax L.J. 260 (2009).