If any other evidence is needed that this howl from the Catholic prelates is politically motivated consider this little factoid.  De Paul University, the largest Catholic university provides birth control to their employees in their health plan.

Catholic hospitals and universities in the 28 states that already require insurance coverage and availability for contraception have complied and never said a word.

So, yeah, this is about the Catholic bishops wanting to pick a fight.  And where, exactly, were you when little boys were being molested?

Finally on the legal argument.  This area of the law has already been litigated and found not to be an infringement on religion.  No one is forcing people to use the pill they are just giving women in an employment setting access to birth control.  This is simple labor law.  Catholic hospitals and universities have to obey child labor laws, and pay workman's comp, and pay overtime if people work past normal working hours.

The key here is that these institutions are in the broder market.  They serve many people who may not be of that faith or any faith, and employee people who come from different faiths or no faith at all.