Right after, Elaine asked if he was sitting at the campfire with them all night, so I actually feel like the whole entire thing might have just been to try to impeach his statement about being "with them all night."
Stupidest decision ever though, because I'm pretty sure the jury understands that statements like "I was with them all night" isn't meant to be 100% literal and I doubt that it really affects the credibility that they give his statement about Amber being the crazy one. So why would they put that in evidence?!
And yeah, TUG obviously chafes Heard's ass, but if they're trying to suggest that there's bias because TUG's tweet happened to be the one that this guy replied to, I think they're barking up the wrong tree.