I don't really get offended by self expression but for a school I'd think it's inappropriate, diverts attention, and most instructors, if not all, wouldn't allow training gear like that. The gi probably wouldn't be a problem since you probably won't see the inside but the shorts, especially when there are kids classes before adult ones, would be an issue.
It strikes me as just corny. When you're training thinking of sex or wanting to see sexual images seems like it would be the furthest things from any dudes mind. Seems like something for an attention hungry dweeb.