But if you read history you know that many beliefs which today are mainstream and moderate did not start out that way.
Jesus, Gandhi and Martin Luther King were all extremists in their day.
Abolitionists were considered radical extremists in the 1850s. William Henry Seward (who later became Lincoln's Secretary of State) was an outspoken abolitionist in the 1850's. According to the New York Herald, "[His] views are those of the extreme fanatics of the north".
I think we should be more concerned with the wisdom and truth of the message rather than how moderate or extreme it is.