I don't think the abuse is crazy at all. It's the result of having witnessed the same shite over and over again while being treated like clueless idiots by the board and Wenger with excuses about stadium debt, ridiculius fees in the transfer market, wages, etc.
If it's excessive it's a result of the actions, or rather inaction from the club and it's leadership over an extended period in which their deficiencies on the pitch have been consistent. How many years in a row have people said they need a top class striker, steel in the middle of the pitch and in the backline and a strong voice in the dressing room to lead them?
If you have to witness that crap year after year, while your relatively valid concerns are dismissed as reactionary nonsense being driven by outside factors rather than the football you're watching week in, week out for over a decade then eventually this type of reaction is the result. It's over the top, but I don't think it's crazy or hard to understand. When people feel frustrated about a power structure they feel doesn't care or listen to their concerns then they will lash out, often at targets that aren't the source of their discontent.
The board and Wenger are the ones responsible for creating this atmosphere and allowing it to fester to this degree. Even if you'd want and expect better of people we know that's not how it works, unfortunately.