I would hardly ask a Jewish rabbi to comment on the validity of Christian belief but if he's authoritative to you for interpretation of Paul's writings, which he calls “spurious”, then you'll love his comment on the Last Supper.
“Still more is the partaking of the bread and the wine of the communion meal, the so-called “Lord's Supper,” rendered the means of a mystic union with Christ, “a participation in his blood and body,” exactly as was the Mithraic meal a real participation in the blood and body of Mithra”
I.e., the Last Supper is the equivalent of the Mithraic worship and vice versa.
The Pharisees hated Christ and did all they could to discredit him and his teachings and their spirit lives on today.
You don’t like that source? How about wikipedia?
___________________________________________________________
Authorship
Paul Writing His Epistles, 16th century (Blaffer Foundation Collection, Houston, Texas).Paul’s letters are largely written to churches which he had visited; he was a great traveler, visiting Cyprus, Asia Minor (modern Turkey), mainland Greece, Crete, and Rome. His letters are full of expositions of what Christians should believe and how they should live. He does not tell his correspondents (or the modern reader) much about the life of Jesus; his most explicit references are to the Last Supper[1 Cor. 11:17-34] and the crucifixion and resurrection.[1 Cor. 15] His specific references to Jesus’ teaching are likewise sparse,[1 Cor. 7:10-11] [9:14] raising the question, still disputed, as to how consistent his account of the faith is with that of the four canonical Gospels, Acts, and the Epistle of James. The view that Paul’s Christ is very different from the historical Jesus has been expounded by Adolf Harnack among many others. Nevertheless, he provides the first written account of what it is to be a Christian and thus of Christian spirituality.
Of the thirteen letters traditionally attributed to Paul and included in the Western New Testament canon, there is little or no dispute that Paul actually wrote at least seven, those being Romans, First Corinthians, Second Corinthians, Galatians, Philippians, First Thessalonians, and Philemon. Hebrews, which was ascribed to him in antiquity, was questioned even then, never having an ancient attribution, and in modern times is considered by most experts as not by Paul (see also Antilegomena). The authorship of the remaining six Pauline epistles is disputed to varying degrees.
The authenticity of Colossians has been questioned[46] on the grounds that it contains an otherwise unparalleled description (among his writings) of Jesus as ‘the image of the invisible God,’ a Christology found elsewhere only in John’s gospel. On the other hand, the personal notes in the letter connect it to Philemon, unquestionably the work of Paul. Internal evidence shows close connection with Philippians[47]. Ephesians is a very similar letter to Colossians, but is almost entirely lacking in personal reminiscences. Its style is unique. It lacks the emphasis on the cross to be found in other Pauline writings, reference to the Second Coming is missing, and Christian marriage is exalted in a way which contrasts with the reference in 1 Cor. 7:8-9. Finally, according to R.E. Brown, it exalts the Church in a way suggestive of a second generation of Christians, ‘built upon the foundation of the apostles and prophets’ now past.[48] The defenders of its Pauline authorship argue that it was intended to be read by a number of different churches and that it marks the final stage of the development of Paul of Tarsus’s thinking. It has to be noted, too, that the moral portion of the Epistle, consisting of the last two chapters has the closest affinity with similar portions of other Epistles, while the whole admirably fits in with the known details of St. Paul’s life, and throws considerable light upon them[47].
Russian Orthodox icon of the Apostle Paul, 18th century (Iconostasis of Transfiguration Church, Kizhi Monastery, Karelia, Russia).
Saint Paul, Byzantine ivory relief, 6th - early 7th century (Musée de Cluny)The Pastoral Epistles, 1 and 2 Timothy, and Titus have likewise been put in question as Pauline works. Three main reasons are advanced: first, their difference in vocabulary, style and theology from Paul’s acknowledged writings; Defenders of the authenticity note, that they were then probably written in the name and with the authority of the Apostle by one of his companions, to whom he distinctly explained what had to be written, or to whom he gave a written summary of the points to be developed, and that when the letters were finished, St. Paul read them through, approved them, and signed them[47]. Secondly, the difficulty in fitting them into Paul’s biography as we have it.[49] They, like Colossians and Ephesians, were written from prison but suppose Paul’s release and travel thereafter. However, Christianity was not yet declared a religio illicita at the time they were written, and according to Roman law there was nothing deserving of death against him[47]. Finally, the concerns expressed are very much the practical ones as to how a church should function. They are more about maintenance than about mission[citation needed].
2 Thessalonians, like Colossians, is questioned on stylistic grounds, with some[citation needed] noting, among other peculiarities, a dependence on 1 Thessalonians yet a distinctiveness in language from the Pauline corpus. This, again, is explainable by the possibility of St. Paul requesting one of his companions to write the letter for him under his instructions[47].
Or, from Answers.com:
The apostle Paul wrote the Christian religion’s earliest texts while crisscrossing the Mediterranean and preaching about the divinity of Jesus of Nazareth. Paul’s letters to other believers — declaring that Jesus had risen from the dead and was the Christ, the anointed one, foretold by Jewish prophets — are now a vital part of the New Testament of the Bible, and his words have strongly influenced Christian thinking and worship. Paul himself did not start out as a Christian believer. According to the biblical book The Acts of the Apostles, he was originally known as Saul and was an authorized persecutor of the followers of Jesus. He suddenly converted, Acts says, after being temporarily blinded by a flash of light and hearing the voice of the risen Jesus while on the road to Damascus. Taking his new name of Paul, he became a traveling Christian leader, explaining the movement to the Greeks, starting new churches, and settling conflicts in existing ones. He was jailed or run out of town many times for angering local religious and civic leaders. Scholars say Paul was the actual writer, in Greek, of seven biblical epistles: Romans, 1 Corinthians, 2 Corinthians, Galatians, Philippians, 1 Thessalonians and Philemon.
Paul is considered a saint in Roman Catholic, Orthodox and some other Christian traditions... His hometown, Tarsus, is in modern-day Turkey, in a region then known as Cilicia... Unlike other famous Christian disciples, Paul never met Jesus before his death. Like them, however, he took the title “apostle” (Greek: apostolos), meaning “one sent forth”... Most scholars question Paul’s authorship of six more biblical letters attributed to him: Ephesians, Colossians, 2 Thessalonians, 1 Timothy, 2 Timothy and Titus. They differ from his other epistles in style, viewpoint and vocabulary. Their unknown authors may have identified with Paul’s school of thought or hoped to invoke his authority... Among Paul’s most famous passages is the discourse on love in 1 Corinthians 13. It begins, “If I speak in the tongues of mortals and of angels, but do not have love, I am a noisy gong or a clanging cymbal,” and ends, “Now faith, hope, and love abide, these three; and the greatest of these is love.”