"my family is decidedly middle-class"

Why are you so sure? What are the numbers? It's possible you're in a middle income bracket within a rich region, but if you're shopping at Apple and Williams Sonoma on the regular, I'd guess that puts you in the top 20%. I guess we have to define middle class too...maybe the 25%-75% household income bracket?

According to https://siderea.dreamwidth.org/1237182.html

"In the US, we have a rule: to describe a person as "lower class" is an insult; less obviously, to describe them as "upper class" is as well. To describe something as "lower class" or "upper class" is to denigrate it, and to attribute a "lower class" or "upper class" thing to some one is to denigrate them. It is the designation "middle class", alone, which is virtuous – a fact which explains in a nutshell why, famously, all Americans arrogate the term to themselves."

This is the reality, but of course it's absurd. I'm going to be brave and admit I'm not middle class from now on, though I'm sure all my peers would easily accept any claim that I am.

we are in the top 15% I think? which I guess puts us in the upper middle class ? We aren't 'high income', for sure, we make a bit south of $130,000 / year jointly.

I think they could be pretty darn sure if their income was between $55k and $65k since that's right around the median.

The root of the problem of definition here is that there is no concrete definition of "middle class". Median income is related, but not required to be middle class. Besides, in San Francisco, making less than $59k per year is considered poverty level, and $100k+ is still "low income" [0].

[0]: https://www.bbc.com/news/world-us-canada-44725026