The significance of St. Paul's conversion is lost on many.
He was a truly evil man with no redeeming qualities. He would remain, by his own admission, a very sinful man, yet God would use Paul's flaws to spread Christianity throughout the world.
God HAS also done this with abortionists and to ignore this would be sinful on our part.
From everything I've read, Saul was very sincere in his actions. He truly believed he was doing God's work. I think that's why he needed to meet God face to face.
It's eerily similar to how modern day converts from Islam report Jesus appearing to them and calling on them to repent.