That depends on how you want to define "liberal in a classical sense." Blum wasn't a libertarian, which is how many people would define the term nowadays, more of a liberal in the mould of the two Roosevelts.
I think the best and most concise yet general definition I have come across is "one with an open mind but not an empty head." It is quite possible to be a liberal in the classical sense and to cherish our freedoms accordingly without being a libertarian, particularly with respect to foreign policy.
Like it or not, the United States were for a long time a force for mainly good in the world. As that changes based on adoption of largely internationalist ideologies and minimization of our military power, we concurrently forfeit our domestic freedoms. See generally, the United Nations and increasing Obama Administration reliance upon it rather than asserting what should be our own foreign policy. See also, UN arms control treaty efforts.
Mr. Blum was a Democrat and supported Democrat candidates. That support never, as I recall, became a part of his lectures or of our assigned reading materials (of which there were many). I remember fondly his introduction of Barry Goldwater (who later became the 1964 Republican candidate for President), whom he had invited to speak to our history class. We welcomed Senator Goldwater with loud applause.
There once were, and may still be at least a few, Democrats capable of being "open minded but not empty headed." That is a condition to be commended and encouraged.