it's sad that one should have to actually read what this statement entails, as it's pretty straightforward.... "Suck my fart" is a wish from a person that dislikes another to suck his or her fart. It could probably be incorporated in fetishistic sexplay, if that's your thing. Barring that situation, this is inherently insulting, as it's understood that no one would like to suck anyone else's fart. It's thought to be a wholly unpleasurable, and degrading experience. Originally, it's been utilized as a play on the old adage " eat my dust", or the take offered by the famous "Flo" on the hit TV series "Alice": "Kiss my grits".
version one: "i hate you, so suck my fart"
version two "I love you, would you like to suck my fart?"
version three* "doctor, would you do me the kindness please and suck my fart outta my ass, . my anus burns... it BURNS, doc! Christ it BURRRRRRRRRRNS!!!!"
*this is a rare usage, but still holds true.