I don’t disagree with you about cutting off diseased branches - and I have NO issues with colleges and/or national orgs cutting off those diseased branches quickly. My S’s chapter was on probation for something I consider very minor, but it was technically in violation of the university’s law. Well, ok, then. Take your lumps. I have no problem with the punishment they received.
I guess here’s another analogy: A college may have several student newspapers - maybe one is the mainstream campus and city news, one is from a conservative point of view, one is from a liberal / progressive point of view, one is humor / satirical, etc. Maybe there is some association of those newspapers from the perspective of issues that affect all of them (access to printing facilities? distribution channels?) - but the mainstream and the progressive and the humor one don’t really have the “right” to kick the conservative one off campus if the conservative one “misbehaves” - that would presumably be the job of the university. Make sense?
I think when people talk about “the Greek system” they need to understand that there really aren’t that many commonalities between the Sigma Chis and the Sigma Nus institutionally, so to TG’s point, if the Sigma Chis say the Sigma Nus should be kicked off campus, it’s sort of a “great, what business is it of yours.”