Honestly, I wonder what kind of an atmosphere could allow this kind classless demonstration to occur. If I was sitting in the stands and the guy next to me started booing to try to throw someone off, I would tell him to shut up. In tennis, they had people escorted away from the stands for the same behavior, but I guess there was just too many for the officials to handle in the case of the polevault. If I were a competitor, I would signal the fans to cease this behavior. It's not in the spirit of sportsmanship to be happy to win while the crowd is actively trying to interfere with your competitors.
I'm not trying to be some kind of fascist and demand an apology from da Silva the Brazilian, but can we at least all agree that he should have condemned this behavior?