His position is summarized in the following two paragraphs:
I think that polyamory—multiple consenting partners—is a relationship style that can work well for some people in some life situations. If you want to prioritize freedom (keep your contracts minimal and short), variety (of personalities you interplay with), or exploration of types of partnerships, it might make sense.
However, if you wish to prioritize true love (depth of intimacy with a hopefully forever partner) or a stable family, I think polyamory is a style which is at best deeply challenging and at worst fundamentally opposed to those goals. So I want couples with these priorities who are considering polyamory to make sure they aren’t ignoring the tradeoffs in a setting where the cost of failure is significantly more than a broken heart.
His position is summarized in the following two paragraphs: