I've read this quote multiple times, over the years:

Conservatism consists of exactly one proposition, to wit: there must be in-groups whom the law protects but does not bind, alongside out-groups whom the law binds but does not protect.

It turns out it's from a comment on a blog post moaning about liberals: https://crookedtimber.org/2018/03/21/liberals-against-progressives/#comment-729288

The rest of the comment is a lot more interesting than the pithy quote, because it cuts through a lot of the usual noise in leftist discourse.