Can't make this stuff up. Tech foul

[phansen]

A1 is on a break away lay up. B1 is chasing from behind. As A1 goes up for the layup, B1 reaches down with both hands to A1's shorts and attempts to pull them down. B1 doesn't get a good enough tug and A1 scores the basket.
I counted the basket and gave B1 a technical foul. Opposing coach wanted an intentional foul which I don't think is right. I told B1 he was making a travesty of the game and that was what the foul was for. He didn't argue but looking in the rule book I would have probably went with 10-3-6 and just say it was an unsporting foul.