The members of the Westboro Baptist Church are despicable. Their message of hate is monstrous and indefensible and has no place in society. And yet, by taking away their ability to speak it, we've all lost something more important.
Said "church" is infamous for their acts of picketing military funerals. This has been universally and justifiably condemned, to the point that many state legislatures have passed laws prohibiting any protests at funerals. I think that this is a mistake.
The First Amendment wasn't meant to protect popular speech because words that everyone agrees with don't need protection. It was meant to provide explicit protection for words and ideas that the majority hates and would prefer to silence. Westboro's speech clearly falls into the latter category, and we should all defend their right to say it while speaking out against the words themselves. There are times when we all want to say things that most people would disagree with, and we can't expect that freedom for ourselves while taking it away from others.
Beyond that, though, I believe that their ability to protest is more important than their words which we all pretty much ignore. Westboro is saying bad things about good people, about men and women who voluntarily died for their country. However, it's possible that you and I might someday want to say bad things about bad people, and I'm not sure that it's possible to pass a law against the first without restricting the second.
As an admittedly unlikely example, suppose that some country wanted to give a state burial in honor of Adolf Hitler. Almost everyone would agree that this would be a horrible idea. In particular, quite a few organized groups would probably want to plan protests and demonstrations during the funeral to express exactly how much they opposed it. I think that a majority would support their right to do so and wouldn't dream of passing a law to prevent those protests. How do you phrase a law so that it allows decent people to protest at Hitler's funeral but keeps disgusting people from protesting at an American soldier's? You can't say that you can only picket against unpopular or unliked people; Martin Luther King, Jr. had quite a few enemies in certain places while Joseph Stalin still has pockets of admirers to this day. Besides, the last thing we want is the government dividing people into "good" and "bad" categories and providing protection to one but not the other.
I don't have an answer for this dilemma. As much as I detest the members of the Westboro Baptist Church for preaching hate in the name of God, I honestly don't know how we can justify silencing them just because we don't like their message. As much as I disagree with them, our Constitution and our founding principles declare that they should be allowed to say their piece, wretched as it might be.