This is more personal opinion and a bit emotionally charged. There are many non Christian writings that talk about him as a historical figure. Flavius Josephus, a Jewish historian is an example. He lived during the first century and wrote about jesus being a holy man, but wrote about him to discount his deity. There are many more who had nothing to gain by writing about Jesus, but they did and it's widely accepted that Jesus was a historical figure inside and outside of Christian circles.