England was not the first government in the modern world to criminalize the slave trade. That distinction belongs to the Commonwealth of Virginia, which outlawed the practice in 1778 – twenty-nine years before Wilbur Wilberforce's bill became law.
Virginia also passed legislation four years later in 1782 which encouraged emancipation. That legislation went so far as to require slave owners to support their emancipated slaves who might not be able to sustain themselves in a gainful occupation. The slavery question continued to come up for debate and public discourse until Thomas Jefferson’s grandson, Thomas Jefferson Randolph (pictured here), introduced legislation in the House of Delegates in 1832 that would have ended slavery in Virginia. He proposed an idea that had originated with his grandfather (Thomas Jefferson), a proposal that had been defeated by the General Assembly in 1779. Randolph suggested that every male slave born after July 4, 1840, be granted his freedom upon his twenty-first birthday. The legislation would grant the same freedom to female slaves upon their eighteenth birthday. Randolph’s bill was defeated by only a “small majority.”
In fact, the Reverend Randolph McKim (1842–1920), a Confederate chaplain and one-time rector of Christ Church in Alexandria, wrote in A Soldier’s Recollections that Randolph assured him in 1860 “that emancipation would certainly have been carried the ensuing year, but for the revulsion of feeling which followed the fanatical agitation of the subject by the Abolitionists of the period.” And although the bill was defeated, the Virginia legislature “passed a resolution postponing the consideration of the subject till public opinion had further developed.” An editorial in the March 6, 1832, Richmond Whig praised the legislature’s efforts and further noted: “The great mass of Virginia herself triumphs that the slavery question has been taken up by the legislature, that her legislators are grappling with the monster, and they contemplate the distant but ardently desired result [emancipation] as the supreme good which a benevolent Providence could vouchsafe.”
(From a previous post.)
Obviously, the slavery issue is more complicated than this short post addresses, but suggesting that radical abolitionist agitation did not negatively impact Southerners' attitude is silly.