Out of all the various Jewish parties that flourished during the Second Temple period, only the Pharisees survived the Jewish-Roman war as an identifiable continuing entity. The semi-monastic Essenes eventually died out, the Sadducees were all but wiped out in the fall of Jerusalem and the last of the Zealots were crushed at Masada.
The Pharisees are in a very real sense, the fathers of modern Rabbinic Judaism and this is affirmed without apology by modern Jewish scholars:
"Pharisaic Judaism became normative Judaism. Its principal features — the synagogue, the rabbi, prayer, Torah study, and belief in the oral law — became the modes of religious expression guiding Jewish life ever since. All Jewish life today, therefore, stems from the Pharisaic tradition and derives its central religious characteristics from it." (Eckstein, Yehiel, What Christians Should Know About Jews and Judaism. Word Books 1984, p. 258.)
It's certainly true that Jesus had sharp disagreements with Pharisees, but you have to understand that at the time there were two competing schools of Pharisaic thought. These were the liberal Bet Hillel and the hardline Bet Shammai. In Rabbinic literature, one story goes like this:
"A Gentile came to Shammai with the strange request that he be taught the entire Torah, but that it be done during the time he could stand on one foot. Shammai, a surveyor by trade, chased him away, swinging a cubit stick. When this Gentile approached Hillel with the same request, instead of being scolded for such an impudent demand, he was told, "What is hateful to you, do not to your fellowman. This is the entire Torah. All the rest is commentary — now go and study.""
The parallels with Hillel’s statement are readily recognized in Jesus’ statement in Matthew 7:12 and Paul’s "summary" in Galatians 5:14. Hillel's negative formulation of Jesus' Golden Rule is sometimes referred to as the "Silver Rule". It, in turn, is derived from even earlier Jewish tradition: "Do to no one what you would not want done to you." (Tobit 4:15)
In the controversy stories, Jesus time after time, advocates the position of normative Judaism. Who and what he was actually arguing against has been lost in history and is very perplexing today:
"The case is more dubious for Matthew, a gospel which is commonly dated in the 80's or 90's at a time when the Pharisees appear to have risen in prominence and power (though to what extent remains debatable), and a time when the relationship between Jews and Jewish Christians collapsed. That late first-century setting provides a possible Sitz im Leben for Matthew's gospel, which suggest to many scholars that rather than providing historical information about the Pharisees of Second Temple Judaism, Matthew's portrayal of the Pharisees is really a representation of the Jewish leadership toward the end of the first century." (Neusner, Jacob; Chilton, Bruce In Quest of the Historical Pharisees Baylor University Press 2007 p. 67)
"The Pharisees never included healing in their list of activities forbidden on the Sabbath; and Jesus’ methods of healing did not involve any of the activities that were forbidden. It is unlikely that they would have disapproved, even mildly, of Jesus’ Sabbath-healing. Moreover, the picture of bloodthirsty, murderous Pharisees given in the Gospels contradicts everything known about them from Josephus, from their own writings, and from the Judaism, still living today, which they created..." (Maccoby, Hyam Revolution in Judea: Jesus and the Jewish Resistance Taplinger Publishing Co. 1980 pp. 11-12)
"It seems that the Evangelists had little idea about the details of Jewish laws, and only by careful analysis can we establish what lay behind their words. We must note that in all cases in legal debates about Sabbath in the Synoptics, the question of dispute revolves around scribal laws and whether or not the questioning Pharisees know these laws as well as they think they do. The debate about eating in the fields is of this order too. When people pluck out grain, if they then push out the kernel of wheat which is an unusual or rare circumstance (normally wheat is harvested in large amounts with an instrument) they do not violate biblical Sabbath rules." (Basser, Herbert W. Studies In Exegesis: Christian Critiques of Jewish Law and Rabbinic Responses 70-300 C.E. Brill 2000 pp. 26-27)
"It is an amazing fact that, when we consult the Pharisee law books to find out what the Pharisees actually taught about healing on the sabbath, we find that they did not forbid it, and they even used the very same arguments that Jesus used to show that it was permitted. Moreover, Jesus' celebrated saying, 'The sabbath was made for man, not man for the sabbath,' which has been hailed so many times as an epoch-making new insight proclaimed by Jesus, is found almost word for word in a Pharisee source, where it is used to support the Pharisee doctrine that the saving of life has precedence over the law of the sabbath. So it seems that whoever it was that Jesus was arguing against when he defended his sabbath healing, it cannot have been the Pharisees." (Maccoby, Hyam The Mythmaker Paul and the Invention of Christianity Barnes & Noble Publishing 1998 pp. 33-34)
I respect a lot of the Christians here, but for crying out loud... You do realize that what the JW's taught you about the Jews, Pharisees and the Law was utter nonsense?