Although not published until 1866 (by William Dugdale, famous in his day for publishing pornography), the English poem Don Leon first surfaced in 1833. The poem is a long apologia for homosexuality and is attributed to Lord Byron, who is universally believed not to be the author (the true author remains unknown, with Byron’s friend George Colman the likeliest candidate). It is one of the earliest pieces of English literature explicitly calling for tolerance of homosexuality.
The poem begins by invoking famous men tied to recent gay scandals – including William Thomas Beckford – and goes on to extol the virtues of love between men, mentioning in turn men whom Byron was rumored to have had romantic relationships with, including John Edleston and Nicolo Giraud.
You can read the the poem in its entirety here.