Well, he pretty much pranked Dylan but then again, Dylan also got pranked by Dolly and Dawkins earlier in the season. As smart as he is, Dylan is one of those characters whose very easy to trick and he's a terrible judge of character (Bessie and Hunter...). He can also come off as rather condescending at times (Dal-Martians, Wow Of Miaow) and I think the reason Dante tricked him is because Dante saw him as disrespecting the dead by playing with those bones. Graverobbing's not a cool thing to do.