When you read the entire article, you find that he was not arrested for being in a stall with a friend. There was violent behavior which started when he was told he couldn’t be in the stall with his friend.
Koenig and Heider attacked the attendent, and then they left the bathroom, where they continued acting in a beligerant manner.
Actually, though, he wasn’t arrested for the violent behavior. He was arrested for violating a domestic no-touch order, because he was at the fair with his girlfriend who he wasn’t supposed to have any contact with because of prior domestic violence. Oddly though, she was there willingly, and she was arrested for interfering in his detainment.
And the article gives NO clue as to what they were doing in the stall. I would have said drugs, but I’d assume the police searched both men and found nothing, or it would be in the article.
If it was drugs I imagine they would have flushed any evidence once they realized they had attracted attention.