YOU can launch as many campaigns as you want. You can take a knee, raise a fist, or pointedly refuse to do either.But the only way to ensure social media companies tackle racist abuse is for the game’s big hitters to join the boycott led by Swansea and Birmingham.So vast is the income of Instagram, Facebook and Twitter that it is difficult to quantify the monetary value of Premier League teams and their players. But it is certainly not inconsequential to companies for whom 98 per cent of revenue is derived from advertising.Engagement - that’s views and clicks - is the...