An atheist who considers the gospels to be nothing more than urban legend can nonetheless apply the lessons and morals of the New Testament to modern life.
^^^^Quoted for truth.
There's a LOT of really good stuff in the New Testament. A lot of really good ways to live. Whether Jesus was real or not or whether Jesus said most of the things attributed to him matters not one whit to the moral impact of the teachings.
NOW, that being said, Wikipedia Scholar Cypress has a valid point that it IS fun to find evidence that famous people of antiquity actually existed.
When I go to Paris for work I love to go to St Denis north of the city and visit the Basilica (first Gothic Cathedral in Europe!) and I KNOW that likely St. Denis ACTUALLY EXISTED. But it's pretty easy to dismiss the stories that after he had his head cut off he picked it up and walked to the site of the current basilica and asked that a church be built there.
It's the same sort of thing. Yeah, it's SUPER cool that St. Denis was real, but the stories are clearly NOT.
No Christian has any need to compete with any other faith or set of beliefs as to how "well attested in writing" Jesus is for the message to continue resonating.
To be fair to CHRISTIANS it is ABSOLUTELY IMPERATIVE that Jesus be 100% real and "as advertised", a god-man. The stories are critically true. The coming back from the dead etc.
So to that end sometimes the moral teachings take a back seat.