Why shouldn't health insurance cover birth control if it covers Viagra?

Sens. Kay Bailey Hutchison and John Cornyn signed a letter to Dept. of Health and Human Services Secretary, Kathleen Sebelius this week complaining about the department’s implementation of the Institute of Medicine's (IOM) recommendation to include birth control as a required part of health insurance.

The Senators say they are concerned "with the lack of due consideration given by [Sebelius] and your Department to the adverse impact that IOM's recommendations would have on our core constitutional value of religious liberty." The Senators stated that "[t]hough the IFRs' 'religious exemption' purports to protect religious organizations, health care professionals, and health care plans, it is clear that this protection falls well short of securing this constitutional right."

In other words because some fundamentalists feel there is a biblical prohibition on birth control in any form health insurance companies shouldn’t be required to cover it. Shouldn’t the logical extension of their argument be that if God wanted a man to procreate the man wouldn’t need Viagra therefore insurance shouldn’t cover it? Why haven’t we heard a tremendous uproar about prohibiting insurance from covering Viagra I wonder?