I guess this is a version of the “unnatural acts” argument against homosexuality:

A member of a religious group campaigning against homosexuality holds a sign saying “Anus 4 Defication[sic]” during a rally in Kampala, Uganda in 2007
(source)
Around the same time, these people were protesting against nose picking, soccer and several other multifunctional interpretations of the usage of human body parts.
While I find this hilarious as an outsider, I understand the joke is lost on victims of homophobia.
More on homophobia, gay rights in Uganda, and gay rights in general. More protest signs. More jokes.