I found this helpful article— Looking for Legalism, Finding Hypocrisy — in the November Adventist World. If the author had intensions to address erroneous attitudes about Judaism, he kept it below the radar. However, he did a nice job of undermining one of the key accusations thrown at Judaism— legalism.
The author, Joseph Olstad, summarizes the problem nicely.
I read and hear the contours of this model everywhere—in Sabbath schools, sermons, periodicals, and casual conversation: “Pharisees were legalists and were teaching legalism”; “Jesus rebuked the Pharisees’ legalism and taught us a new way of grace and love”; “Christians should obey the law but not legalistically”; “Obeying the Sabbath is legalism”; and so on. Within this paradigm it seems that legalism is a major threat in the Gospels; therefore, Jesus’ rebukes and teachings are seen as correcting that problem.
I have noticed that the Pharisees are often the favorite whipping boy in Sabbath School discussions. I doubt that many of those making these statements are aware that Rabbinic Judaism is the direct descendant of the Pharisees, but I think unconsciously the connection is made— the Pharisees practiced legalism and so does Judaism.
The article speaks for itself, so I won't say much more about it. However, we shouldn't forget that Paul was a Pharisee and continued to claim Pharisee identity to the end, and it seems likely that many of the “Pharisee party” described in Acts 15 were among the “tens of thousands” mentioned in Acts 21 who were zealous for the Torah. We should not assume that hypocrisy or legalism were necessarily an aspect of the Pharisee way of life.