Arsenal as a football club is a very different thing to the Arsenal fanbase, and certainly not related to the morons that abuse football players on social media.
Therefore, Granit Xhaka being abused on Twitter is no reflection whatever on Arsenal, neither the football club, nor the fanbase for that matter.
The club generally act with more class than other clubs in their dealing with supporters, players, managers and other clubs. That reputation has been forged over decades.
Xhaka, as captain of the club, trudged off the pitch at the Emirates at a snail's pace, throwing a tantrum because he both didn't like being subbed and because a few thousand fans were happy about it, in a game when we were losing, off the back off a terrible run of bad results; the fans told him to get off the damn pitch quicker in no uncertain terms and he told them to fuck off; instead of apologising after the heat of the moment he decided he was going to cowardly use the excuse that "Arsenal fans" had abused him on twitter to justify his actions.
Good fucking riddance.