Exactly, on Twitter I've read it's only chewing gum. It didn't matter what it was it shouldn't happen, if any thing chewing gum is worse depending on the mouth it's been in.
Also, some suggested the linesman went off a bit later after the incident with a leg / hamstring injury and it wasn't related to the incident. How do they not know if he hasnt been intimidated and uncomfortable about the situation and didn't feel he could carry out his job to his best abuilty.