like-minded people congregating before the existence of christianity - fact
flood myths that predate the biblical flood myth - fact
tales of virgin birthed miracle performers that resurrected after death that predate jesus - fact
winter solstice celebrations that predate christmas (that involved trees, feasts, and gift giving) - fact (Christmas is seen as so pagan/unbiblical in the eyes of some Protestant groups that the celebration of the holiday was actually banned)
your opinion that these facts are just opinions - false
Just to note, a writing based on an alleged event that was "predated" by a writing before it is hardly evidence of direct borrowing, as you're suggesting.
For instance, there are tons of works written about MLK, some ranging from 1960 to 2010. Using your flawed and obviously prejudice logic, any work written after the 1960 work clearly borrowed from the work written in the 60's, so those can be discounted as plagiarized. Of course, without even looking into any evidence, you'd assume that any book written after 1960 on MLK is original...not because you've examined them all, but because they aren't
religious in nature.
There are so many "flood myths" and so many works like there are on MLK, that the similarities are really coincidental, since they cover the same event(s) in question
Just sayin', the "predated" argument
alone as evidence has long been dismissed by any serious historian of antiquities.