MSM folk don't like reporting when POC behave badly. In this case the chants probably were heard in TV coverage - as well as by US spectators - and there are enough Portuguese-speaking people in the US that keeping a lid on these Brazilians' crude behavior was not possible. So they reported it, without details that would show just how crude they were being.
That's my cynical speculation. Maybe the Sentinel just didn't have anyone able to translate Portuguese.