Some of the old liberals may have supported progressive taxation and some opposed it John Stuart Mill opposed it Again just as in public education being for or against progressive taxation is not what makes someone a classical liberal You ask what standard should be used The standard to be used is the SOURCES who tell us what classical liberalism is I don t know why you would expect early liberal to have an identical philosophy Look at someone today is who is called a conservative It shouldn t be any problem to find things that some of them support that would be considered inconsistent with conservativism The conservative philosophy stands as distinct from the philosophy of every individual who is considered a conservatives Defining conservativism isn t grouping together EVERY position that EVERY conservative has held It would be a nonsensical and internally contradictory definition Likewise for classical liberalism Secondary and tertiary sources tell us what classical liberalism is I imagine they find the positions that MOST of them hold