Here's a quote from Benito Mussolini:
"Fascism is for liberty. It is for the only kind of liberty that is serious—the liberty of the State.”
(Source: The Ominous Parallels by Leonard Peikoff; Chapter: "The Totalitarian Universe")
Progressivism is a milder form of fascism, so it is not surprising that the progressives have contempt for the constitution.
They think that the laws are meant to regulate the activities of the common citizens, and that the ruling elite must be allowed to get away with any crime.
Brave New Village: Hillary Clinton and the Meaning of Liberal Fascism