I'm assuming you don't watch the show, probably not a brazilian guy... so I will try to explain
Arthur have a weak personality, a visible lack of charm... and seems to be insecure as hell lol
A woman dismissed him and just started to flirt with Fiuk (pictured)...
some will say Fiuk is not equally good looking, he's a skinnier rocker type, I think he's occasionally charismatic and charming (I said before that "take Fiuk instead of Arthur" was a dumb move, but I don't think that's absurd anymore)
Arthur just spent some time saying bad things about Fiuk, calling him retarded, etc.. he just have a giant ego / strong sense of entitlement... it's like he thinks he deserves to be treated like a god just for being fit and good looking
Not to say that Arthur and Projota thinks they are the GREATEST PLAYERS of the Big Brother game, but they're like Pinky and the Brain segment in Animaniacs cartoon (Arthur is Pinky)