How to debate Shapiro on Jesus existence:
1- ask Shapiro to explain his beliefs: do you believe old testament is, in majority, the narration of historical facts? Talmud is above the old testament?
2- ask Shapiro if he beliefs are held by faith alone, tradition or if he uses actual scientific evidences to support his beliefs
3- ask Shapiro to explain what would he do in case of discovering his people persecuted and tried to kill his messiah
If you ask someone what would happen if you did not eat breakfast they might say but I did eat breakfast
If you ask Ben Shapiro what he would do if he found out people of Jewish ancestry killed the Jewish messiah then he might say people of Jewish ancestry did not kill the Jewish Messiah