I've never seen this type of behaviour at the Ryder Cup, nor any other golf tournament. I've seen it at football (soccer) matches. It absolutely destroyed the game in the 80s, and continues to plague it till this day. The PGA would be well advised to stomp on that.
The golf itself was fantastic. The Americans almost staged the mother of all comebacks. It was a shame to see their fans walk out en masse when Lowry sunk the ball to retain the cup. The draw was still on at that point, and the players had played heroically, even if they could no longer win the cup. Well, always next time. Just hope the relevant authorities take action to ensure we don't see a repeat of the thuggery.