Yeah, that error has been floating around for a while now; it just won't flush down.
1. God promised to Adam and Eve that He would send a Redeemer. So the idea of a golden age (the Garden of Eden), messed up somehow, rebirth, making things right, redemption -- all pagan nations started out having this idea, which was corrupted over the centuries, as fallen mankind with a darkened intellect is wont to do.
2. The idea that superficial similarities = "it must be a ripoff" is 5 year old child's reasoning. How about super hero movies? You have an average guy (or girl), something happens to him, he gets superhuman powers, has a period of awkward adjustment, then finally accepts the powers as a gift and uses them to fight evil. He ends up with a nemesis of some sort that he continually fights over the years. Sound like every superhero movie or comic book ever? It should.
If you come up with a NEW superhero with NEW powers, no one is going to accuse you of ripping off literally every superhero that has been thought up so far. But if you come up with a superhero with super strength, x-ray vision, capable of flying, who came from a planet that exploded, and is super strong here on earth because of our "yellow sun", and small chunks of his home planet make him weak, and he works for a newspaper wearing thick glasses as a disguise, and changes into a costume with a cape, usually in the confines of a phone booth -- THEN you might be validly accused of copying someone's work!
In other words, the "copying" would have to be much more dead-on to be significant. If major elements are different (which is the case with all the "similarities" between Jesus and various pagan mythical beings), then it's JUST A COINCIDENCE. Broad concepts and ideas are thought of hundreds of times in each century, with no collusion or collaboration necessary.
Is every "Hero's Journey" book or movie copying the others? Countless books and movies have used the Hero's Journey template -- but that doesn't make them all Star Wars.
Death is front-and-center familiar to all mankind. The idea of life after death, or even coming back from the dead, doesn't take a huge amount of imagination. I'm sure more than one person has INDEPENDENTLY thought of it over the years. Ditto for the concept of a virgin birth. People can just THINK of this stuff out of the blue; it's not that complex or difficult.
So if you are after the truth, you have to be fair. Look at the two "stories" and see if one of them is truly influenced by the other -- or are they sufficiently different in key areas so as to make them 2 independent stories, with any similarities being superficial and insignificant.
But a lot of these idiots aren't after the truth. They are after an excuse -- any lame one will do -- to reject Jesus, so they can go back to their bedroom and lose themselves in porn and self-abuse. That's what it always comes down to. Sixth and Ninth. Every. Single. Time.