I hesitate to call the Westboro Baptist Church a cult - I think they are - but I hesitate nonetheless. When a Christian starts calling people names, such as fags, you have to wonder what is going on in their heart. Hell will be full of Pharisees who preached against the sinners of their day, and I suspect that many of the Westboro folks will join the Pharisees in hell one day.
Christians must preach the gospel - with or without the state's permission. And preaching against sin is a part of that. But we should never preach against sin without a tear in our eye, and I don't see that tear in these Westboro Baptist people.
Listen to these words from that latter day Puritan, Charles Haddon Spurgeon:
"If sinners will be damned, at least let them leap to hell over our bodies. And if they perish, let them perish with our arms around their knees, imploring them to stay. If hell must be filled, at least let it be filled in the teeth of our exertions, and let not one go there unwarned or unprayed for."
Recommended reading/listening:
Russell Brand Hosts the Westboro Baptist Church, by David McManus
Sticks and Stones Can Break Your Bones, But Words Can Increase Your Sentence, (my post)
The Roman Road to Salvation, (my post)