Yeah, to me this hinges on how much the shirt looked like Fred Flintstone's outfit. If it was a nice aloha shirt with a repeating triangle pattern in a different color scheme, I think it would be okay? If it literally looks like a cosplay, probably not. And since they switched LW into a T-shirt, it does seem like it probably was closer to the cartoon cosplay side of things.

But also, everyone was being far more belligerent than necessary. It doesn't sound like LW was in the wedding party, so I don't think them being underdressed would Ruin the wedding. But LW was also making things worse (and obviously suing is ridiculous).