It's quite simple. When you hold a referendum with an all-or-none result, that result is going to reflect the prejudices of the majority. Those who are in fairly small minorities, but not inconspicuous ones—the Green Party is one of them—are going to be screwed, essentially, by the process. They're not going to get a fair shake. I think it's a moral decision that things that involve minority rights are not subjected to any kind of referendum. However, as I said, if holding a referendum eases the way to a proportional representation system, it's obviously ridiculous to oppose it.
On September 29th, 2016. See this statement in context.