Of course Tony Scheffler was penalized for this, because the NFL is just no fun and dancing in the end zone is, apparently, excessive celebration. But it doesn't matter. When you're a member of the Detroit Lions and you're leading the New England Patriots by a score of 17-3, you dance your little butt off.
It doesn't matter that it's preseason or that these games don't count. You're a Detroit Lion and this is your year. Get down with your bad self, Mr. Scheffler.