I spent several months attending Quaker (Society of Friends) meetings last year, and in our anti-racism group we learned that it took the Friends some time to come around to opposing slavery, unfortunately. The book Fit For Freedom, Not For Friendship has (exhaustive) details on this and related racial equity issues: https://quakerbooks.org/products/fit-for-freedom-not-for-friendship-4003

One white Quaker abolitionist I learned about and admire is Benjamin Lay. He was disowned and denounced for his views: https://www.smithsonianmag.com/history/quaker-comet-greatest-abolitionist-never-heard-180964401/