I wouldn't be surprised if it was a racist / personal thing that pushed him over the edge. Over years of being in the PL , and especially at places like Spurs & Man U, Viera must have a thick skin and be used to abuse on the pitch. It's a shame it happens, but from understanding it's the worst 'crossing the line' abuse that pushes them over the edge.
Seeing this whole pitch invasion I've got really mixed feelings.
Of course it's worth going crazy celebrating that we escaped relegation. We should NOT be celebrating it, but after such a horrible season at least it feels good. We should be celebrating getting in Europe and winning stuff, and we'll get abuse for celebrating 16th place, when the other lot win 2-4 cups .
On the other hand, I'm surprised that players were not escorted or looked after, and even though our fans are generally great, there's always potential for an idiot, and even our players who have not always been loved could have been under threat. Luckily most people don't repeat in real life what they say behind the safety of their phones & keyboards!