1. Far from retarding the abolition of slavery, the Revolution actually accelerated it. Its triumph gave a big boost to Enlightenment liberalism, which inspired the First Emancipation in the US (the abolition of slavery in the North that became the first large-scale emancipation of slaves in modern history), and boosted antislavery movements in Europe, as well.

2. Had the Revolution been defeated, Enlightenment liberal ideology would have been dealt a setback in Britain and France, too. That would have set back antislavery movements there, as well. It is no accident that many antislavery leaders in Europe were also sympathizers with the American Revolution. The Marquis de Lafayette was just one of the most famous examples of European liberals who actively backed both.

3. The West Indian slaveowner lobby in Parliament was strong enough to block abolition of slavery until 1833. Had Britain also been saddled with the much larger proslavery lobby of the American South, it would have taken far longer. Especially when you combine the impact of the larger slavery lobby with the force of point 2 above.

Here is the full piece, with additional arguuments.