I'm not sure why I hate it either! Something about their use of the word 'ethical,' in 'ethically not interested'. It sounds.... like it's making fun of ethical nonmonogamy somehow? but *how*?
It seems like it's saying that being interested in monogamy is as ethical a choice as non-monogamy, which sounds like a given, except that some non-monog proponents are...preachy. That's how I took it, anyways.