I don't mind Elnenys tweet now, or I wouldn't if it was in isolation, but this suggests he does have a problem with Sanchez (fair enough) and that his World Cup tweet wasn't just friendly banter but was actually an Arsenal player deliberately goading another Arsenal player he doesn't like on social media.
This sort of thing wouldn't have gone unpunished at Arsenal a few years ago, same with the Iwobi party incident. I worry our discipline is slipping.