He went and shushed them. I get it, it’s not much, but he went out his way to do so rather than celebrating with his own fans.
If the game had ended with him stood just in front of them and he fist pumped, fair enough. But he didn’t, he ran across to them to shush them. We would be as livid as them if one of their players did that to us.
Personally don’t mind a bit of craic between players/fans - if fans give it out they should expect it back. But he was intentionally riling them up (which the league is clamping down on anyway).