There's something I think that gets missed every time we have a kerfuffle over this or that offensive thing that this or that pundit said on the air that results in an ad boycott and demands that that person have his/her platform taken away, which inevitably comes pretty uniformly from whichever political cohort tends to vote for whomever the pundit in question tends not to vote for and to encourage his/her audience to not vote for. This is inevitably followed by accusations that one side is trying to rob the other, and particularly the offender, of "free speech" and is "constantly trying to silence" the other side. Quack quack quack. For the sake of illustration, I'll use the current Rush Limbaugh/Sandra Fluke situation.
The main point I want to make is that we need to look at this not through a free-speech prism, but a products-liability prism.
See, Limbaugh's "speech" is actually a product. It's something that he is selling to the public, and more to the point that he is selling to advertisers, who in turn sell their products to the public and use the money they make to buy Limbaugh's product. Limbaugh also sells his product to his employer, which gets its money from advertisers, which get their money from consumers, and so forth. But the point is, it's a product. (The fact that he uses the public airwaves, which neither he nor his employer own, to sell his product is immaterial to this particular point.)
The basic premise behind products liability is that someone who makes and sells a dangerous, poisonous, harmful product is liable for the injuries it causes to those who buy it and to the public at large. The public not only has a right to not buy it, but to persuade others not to buy it either; market forces, together with the law, compel the seller to either take the product off the market entirely or fix it so that it's safe to use or consume. Think of Limbaugh's "speech" as being analogous to asbestos or lead paint. I'm not saying such speech should be outlawed as asbestos and lead paint have been, but asbestos and lead paint are noxious products that were properly taken off the market when they were found to be harmful. Even if they weren't outlawed, no one selling asbestos or lead paint would have the right to expect, let alone require, anyone to buy it.
People like Limbaugh are free to say whatever they want, but they can't force us to purchase what they say, whether directly or indirectly. Their right to free speech doesn't obligate anyone, be they advertisers or consumers, to pay for that speech once it becomes a product. If that product is dangerous, poisonous or harmful, it should be taken off the market.