The problem with the majority of this is a lack of education. I for one grew up and was schooled in England through the mid-90-00's was not taught about England's history in Ireland. I genuinely had very little idea of the scale of the oppression and damage that was caused. The Irish were and are still often painted as some caricature within society. Now when you take that into account many people cannot always immediately understand the position McClean took and the views he holds. I think where the abuse stems from is ignorance of the historical facts, and with a lack of knowledge or education on the matter, your typical football fan/keyboard warrior takes 'offense' and starts with the abuse. I truly believe that if the education system in England was corrected and told us of the atrocities we committed we would have a much broader understanding for why some people think we're dicks (to put it mildly), and any sensible people would see his views on the poppy and say that's fair enough without any further comment whatsoever. It shouldn't be a discussion point, and certainly not one that produces such heated debate.
No one deserves the level of abuse he has had to endure. Likewise, the likes of Tuanzebe and Martial are not deserving of their abuse. Social media companies must enforce ID registration for accounts sooner rather than later. It is the only way to firstly reduce such abuse, and secondly, to remove such people still intent on spouting it from the platforms.