Associating the Sadducees with "liberal" anything seems very bizarre. If anything the Sadducees were arguably the most conservative element of Judaism in the first century--their chief interest was in maintaining the status quo, not ruffling any feathers, and acting as the old guard. They were, after all, comprised of the rich aristocratic priestly families who had, effectively, held the religious (and to lesser extent political) power for centuries. Roman occupation had limited their power and authority of course, but by comparison to the people on the streets, they had far more power.
The Pharisees, by comparison, were basically the Judaism of the every-man, it was the Judaism of the synagogue, of the people in the towns and villages. It was the common man's Judaism. Jesus' criticism of "the Pharisees" had basically nothing to do with Pharisaism itself (Jesus was, all things considered, Himself basically a Pharisee as far as religion is concerned), but instead was with religious hypocrisy and abuses of religion that Jesus takes issue with. That's why Jesus said that one should listen to the Pharisees because they "sit in Moses' seat", that one should do as they say, but not as they do, "because they do not practice what they preach".
-CryptoLutheran