He served as such until 1880, when he was again nominated but refused to take the religious oath of allegiance to the Sovereign.Viewed by some as an outspoken atheist, he declared that he would not participate in any "Christian tomfoolery" and that his word should suffice.Douglas' second son, Lord Percy Douglas (1868–1920), succeeded to the peerage instead.Lord Alfred "Bosie" Douglas, the third son, was the close friend and lover of the famous author and poet Oscar Wilde.In 1866 he was one of the founders of the Amateur Athletic Club, now the Amateur Athletic Association of England, one of the first groups that did not require amateur athletes to belong to the upper-classes to compete.The following year the Club published a set of twelve rules for conducting boxing matches.
As a rider his first winner was in the Dumfriesshire Hunt Club chase in 1865, and his last was at Sandown Park in 1883. He was on the committee of the National Hunt but never won a Grand National as a rider, a last-minute substitution on the victorious "Old Joe" keeping him out of the 1886 National.
Francis was killed in a shooting accident in 1894; the inquest returned an "accidental death" verdict, In February 1895, angered by the apparent ongoing homosexual relationship between Oscar Wilde and his son Alfred, Queensberry left a calling card reading "For Oscar Wilde, posing as Somdomite[sic]" at Wilde's club.
Wilde sued for criminal libel, leading to Queensberry's arrest.
In 1881, Queensberry accepted the presidency of the British Secular Union, a group that had broken away in 1877 from Bradlaugh's National Secular Society.
That year he published a long philosophical poem, The Spirit of the Matterhorn, which he had written in Zermatt in 1873 in an attempt to articulate his secularist views.