Usually hatred from fans is reserved for opposing teams and players. Team A beat Team B so the fans of Team B hate the guy who scored the winning goal for Team A. Makes sense, right? What about hating players on your own team though?
Palmeiras is mired in a terrible run of form that has seen them win just once in their last nine matches so their fans are not very happy with their team. Naturally, they decided to attack and beat one of their own players, Joao Vitor. Sure, he's not even a regular player for them and beating him could only make it harder to win, but beat they did! Makes total sense.
For clarification, that's Vitor in the yellow shirt and that is his friend trying to defend him with a traffic cone. What is missing from the video is Vitor going to the hospital. The injuries were minor and he is fine, but the point remains. These fans are idiots and if they were beat down at the center circle in front of everyone before the next match, I would not object.