Saul was a Jew!
While, we want to learn from the source, particularly as Christians exploring the origins of their religion, the Jews appear determined to obliterate Paul and therefore, Jesus from Jewish lexicon. In the 21st century, it is clear that such a strategy, if true, has failed. Clearly, the rabbis recognize Saul as a rabbi. This confirms his claim to Jewish ancestry in the epistles.
Similar discussions have painted him as the founder of anti-Semitism. Some have attributed the Christianity to his brainwork as he organized his gentile Christians to hate Jews, and to treat Jews with brutality. It is believed that this thesis is difficult to appreciate, and is one of the symptoms of Jewish self-hatred. The question being a need to explain how a rabbi could so aggrieved as to instigate non-Jews to hate Jews. The originators of such theses remain accused of over-protecting the sanctity of the Jewish culture from gentile incursion, and / or pollution. Maybe realizing that nearly one-third of the world population in 2015 claim to be Christians comprised essentially of gentiles is a source of pride that should sweeten the tongues of rabbis.
Saul of Tarsus also became an Apostle
Interestingly, the discussion also confirms that challenging transformation of Saul due to his conversion is historically correct and not a fable. In other words, his conversion marked the turning point for the small Jewish following left by Jesus to transform into a world shaping religion. It is true that angler turned Apostle Peter remained in Jerusalem and interpreted Christianity through the lenses of the Torah, the traits of a learned man in Saul of Tarsus changed the tempo and dimensions of Christianity.
Hence, it appears that there is no rabbi Saul versus Rabbi Joshua contest for the founder of Christianity, but a rabbi Saul, servant to Rabbi Joshua as defined in the Acts of the Apostles. Joshua (as Jesus the Christ) in fact, employs the skills, organization and knowledge of Saul of Tarsus (christened Paul) to market and expand the grace of salvation to the world beyond its isolation and nucleation in Israel.
An Agenda to Suppress
The insularity of Jewish people is astounding. Unusually, it is not ethnocentric in any way; it is just a determination to maintain cultural purity that repels outsiders from learning and knowledge through emblems of distrust. Christian Jews and new coverts to Christianity as easily mocked with labels suggestive of turncoats and traitors reminiscent of Saul of Tarsus. Coming out of such an insular culture apparently sensitizes even messianic Jews from trusting anyone. Somme suggestion is that insecurity makes them suspect a spying ghost in every breadth. Others have accused them of arrogance, simply because the attitude is worrying and defies non-Jewish imagination.
Since, Rabbi Joshua did include non-Jews among His scare-faced followers; Jesus Christ is more acceptable to Jewish thinking because he left Judaism intact. They willingly forgive his criticisms of the various groups and classes. They denigrate the Pope and his Christian church calling a product of Saul's imagination, rather than an intent of Jesus Christ. Further, they claim that many New Testament teachings including the supernatural pre-existent Jesus, Trinity, The Incarnation, resurrection for atonement of sins of the very elect are poignant examples of Paul's creative genocidal mind for the mentally incompetent.

