The Premier League will be bothered, whan this type of behaviour becomes the norm for other clubs, too. The older fans around Europe remember the 80's pretty good. I haven't watched the Everton game last night (I was at some family gathering), but my colleagues at work who have watched the game were disgusted by the scenes at the end. One of them has commented "The hooligans are back at the English stadiums" ...
This is so true.
It's called 'Broken Window Theory.'
It's a bit like if someone dumps a fridge in the back entry, and it doesn't get shifted quickly, other people are far more inclined to add to the mess with their own rubbish. Same with graffiti on walls. You have a clean wall, but someone tags it. You don't paint it out, so others feel it's ok to also tag the wall. Before you know it, you wall is a total mess. If people see a property with a broken window, if so inclined, they will feel it ok to break other windows in the property. That's why it's wise to address neglect and damage quickly, because it sends a subliminal message, just as leaving it leaves the opposite message.
What happened last night, (and in other recent games with some other clubs, I believe) is basically the shit on the doorstep. It needs addressing strongly and quickly, otherwise it sends all the wrong messages out to the utter boneheads who would relish bringing back the darker days of the game. There were two assaults on Palace staff last night. If left unchecked, this is only going one way, and someone will get seriously injured or even killed.
Also, although it might be seen as being a bit of an over-the-top comment here, but these illegal pitch invasions piss all over the memory of the Hillsborough dead. Fans are treated like human beings in stadiums now because of Hillsborough. Human beings are not now caged like feral hyenas, because of Hillsborough. The actions of these utter morons just give weight to those who will inevitably start saying that football fans cannot be trusted anymore, so need caging once more.
All bias aside, I don't blame them one bit for celebrating. It's obvious that many of them were shitting themselves and have been for a while. It's obvious that many genuinely feared they'd go down, hence the cork flying out of the bottle once they had survived. I'm just not sure that illegal pitch invasions, assaulting the opposition, throwing flares into the Palace fans, then rioting on County Road is the best way to go about it. If they are let off with all this carnage, then football cannot complain when others jump on the bandwagon and take us all back to the 80s.