William Lloyd Garrison was a product of the Second Great Awakening, made up largely of Christians who emphasized the New Testament and pursued abolition because they felt it was the moral, Christian thing to do. This explains why Garrison's views on slavery were so clear and uncompromising: he felt it was against God's laws and therefore, had to be abolished by any means necessary. He was unapologetic about this and thought it should happen without delay, so much so that he dedicated his entire adult life to the cause, publishing his paper The Liberator from 1831 until the 13th Amendment was passed.
Since Garrison and other abolitionists were motivated by religion, they felt that violence against slavery and slaveowners was justified, and supported radical actions like John Brown's Raid and later eagerly advocated the Civil War.
William Lloyd Garrison's brand of abolition was based on a liberal Christian conviction that slavery was a moral stain on the entire nation, and pushed for immediate and uncompensated abolition. He famously advocated Northern secession from the Union throughout his life, claiming in his newspaper, The Liberator, that the Constitution, with its protections for the institution, was a "covenant with death." To illustrate his point, he once burned a copy of the document at a Fourth of July celebration in Boston. Garrison, almost uniquely among abolitionists, also advocated women's equality, and in fact, full political, legal, and social equality for freedmen. He also spoke out strongly against colonization, a popular notion among many moderate abolitionists who advocating sending freed blacks to colonies in Africa. While a pacifist, he eventually supported the Civil War, which he came to understand as the only way to end slavery.