...the nonconformist polyamorist who gets an erotic thrill from freaking out the squares and is obsessed with what they think and how they are scandalized...

While I suppose that there must be people who actually think like this, I myself have never met one.

this post, which smugly & uncritically assumes that it stands outside of social norms.

Is it smug and uncritical to point out the existence of a social norm? All I've done is to observe that the norm exists, (very briefly) describe alternatives, and ask "Why do you believe what you believe?" This doesn't seem to be a question you're interested in. While the paradox of choice is well-documented, it is not a linear function. Too much choice can be paralyzing, but we are happier when we can make important choices for ourselves.

It's certainly possible to have non-consumerist justifications for polyamory - Mormon justifications, Muslim justifications, etc.

First, religion is a poor justification for anything. Second, the fact that polyamory is a choice does not mean that a preference for more choice justifies it; the question to be answered is still, "why choose polyamory?" One excellent reason is utilitarian: if polyamory is anticipated to make you and your loved ones happier than any alternative you've considered, why, you should choose it.

Choice is only helpful when it is possible to evaluate one's options by some pre-existing metric. If I were to offer you three closed, unlabeled boxes, allowing you to choose which one to take does not improve your expected outcome.