Still better than the source you originally gave, which was non-existent, or the one you've given now, which is Catholic propaganda.

It might be true that Christmas was not a direct rip-off of Saturnalia per se (though we will probably never know for sure because the Church surely did not go out of its way to record this) but there can be no doubt that both Christmas and Saturnalia are solstice festivals, so at the very least they share a common motivational root. The exact provenance of the details doesn't really matter. What matters is that Jesus was almost certainly not born on December 25, and so whatever the motivation for that date was, Jesus's birth wasn't it.