Wilfried Zaha has called on social media platforms to continue clamping down on racism after Instagram played its part in the arrest of a 12-year-old boy who sent abhorrent abuse to the Crystal Palace forward.Zaha posted the racist messages on his Twitter account on Sunday morning ahead of Palace’s match against Aston Villa, which included the threat: “You better not score tomorrow your black c*** or I’ll come to your house dressed as a ghost.’’The racist abuse was condemned across the board