I became convinced of the Shroud's authenticity after seeing a remarkably balanced presentation of the subject on one of those MSM network shows (60 Minutes, 20/20, or something like that).
At the end of the segment the interviewer asked one of the lead investigators what his conclusion was. The lead investigator was some renowned archaeologist from an Ivy League school (maybe Columbia) who happened to be Jewish. He tried to avoid answering the question by suggesting that he was only presenting facts related to his field of expertise, wasn't brought in to make any solid determinations, etc. But the host of the show didn't let him off the hook.
The guy finally admitted that he could only conclude that this was the burial shroud of Jesus Christ.
"And you're Jewish," the host said.
"Yes," the guy said, in a voice that you could barely hear, "And to be honest with you, I haven't even begun to think of the religious implications of this whole thing."
I’ve never heard of someone, Jewish or not, who argued that Christ never existed. If it really is a shroud of Jesus, it doesn’t really prove anything one way or another (unless you believe that the shroud was created supernaturally, I suppose)