It is easier for a camel to go through the eye of a needle than for someone who is rich to enter the kingdom of God

Often misinterpreted: at this point in time, a “needle” was a gateway into a city, through which merchants were taxed. Not a little metal device with a tiny little eye.

But overall, yeah, the fictional Christ is very much an echo of the real-life Diogenes, who railed hard against social injustice, disparity of rights, and general selfish idiocy.