Tidas knew that something having to do with a fight was going to happen, he just didn't expect his wife to be the instigator. He and Murdoc were discussing possible ways to handle conflict between their two groups when someone called to him.
About twenty seconds after Murdoc walked away, the Highlanders had approached him. At first, it was basic insults about being from Alcon, which didn't bother Tidas in the slightest. When they started talking about his men, he'd become irritated, but still showed no outer signs of being perturbed.
When the men began saying things about his uncle, and started questioning his Aunt Marie's character; Tidas' eyes flared with simmering rage. Seeing that insulting his family was the best way to get a response, they started talking badly about Marco.