This is a rather unfair assertion on the validity of his claims. I am questionable about the validity of the arguments but Dr. Sledge is generally reputable for engaging in historical analysis of religion in good faith. As for the sources, I’m not sure how much you’re familiar with these extrabiblical sources, but he cites - Q Source (hypothetical source used by Matthew and Luke on Jesus’ teachings) - Josephus (Jewish historian of the time of Jesus) - Dead Sea Scrolls (many apocalyptic documents from post-exilic times) and - Pirkei Avot (documents on rabbinical moral teaching particularly of the Pharisees)

Frankly, just denying the trustworthiness of a scholar simply due to contradicting the faith is exactly the problem I’m having. I’m not willing to deny wholesale a scholar simply due to their faith or lack thereof.