By Bonnie Stiernberg On Saturday, rapper Slowthai performed at Montreal’s Osheaga Music and Arts Festival while wearing an anti-fascist shirt that featured a swastika under the word “DESTROY.” The shirt was modeled after the famous 1977 “Destroy” t-shirt designed by punk icon Vivienne Westwood, and its intended message was apparently that we should destroy fascism and bigotry, but in the days since, the musician has learned a valuable lesson: perhaps it’s best to just not wear a swastika at all, ever. After a number of Jewish organizations denounced his decision to wear the shirt (as well as O…