I think the problem in itself is that the art of clanning has changed. I was part of the main community during 09-2012. Fights were much cleaner and there were more clans to engage in battle with. I honestly don't remember hearing of people multi-logging during those years nor do I remember leaks being a common thing. In order to make a short concise point, I don't believe the defense level is the root cause for mains being involved. I think clans are no longer capable of taking a loss. Instead, they will have an arsenal of accounts at any level bracket to win at all costs. I cannot speak for why Main clans would want to rag the pure scene, but I do believe the only way to deal with them is by sending a message (team against crash).
Figured I should add, I do believe a "defense reset" would help revamp the scene. Of course, there will always be 1 defense pures that join clans regardless of the current defense cap. However, I think a defense reset would be good for newer clanning community.