Stiles would never judge her, well, unless she did something that required him to judge her, but she hadn't done anything, so there would be no judging going on here. Just lots of fun. That's it. Something they both obviously needed.
"Really?" he asked as he looked down at his now torn shirt. "That could have been my favorite shirt!" It wasn't but still! Not to mention, she could have just asked him to take it off and he would have.
With Erica draped on him, he pulled his shirt off and then tossed it. No point in keeping it on. After that, he put an arm around her and held her close. "Don't start something that can't be finished."