Can Healthcare Providers be compelled to offer certain services?

Many of the extremists in the pro-abortion movement are outraged at the fact that Catholic hospitals (which constitute a large percentage of American hospitals) refuse to offer abortions, contraception, etc. In many cases they are working to legally compel such institutions to offer these "treatments."

Excuse me? On what basis can the provider of goods be compelled to offer a service? While the law disallows discrimination in who is served, there is no moral or legal basis I know of to force a company to offer a particular good or service. Do I have the right to walk into my local gas station and demand that they sell hard-core pornography? Of course not. And it doesn't matter if they are the only establishment in the area that might offer such "goods"... if they don't want to, they don't have to.

Nor should Catholic hospitals be forced to offer abortions, etc.