Isn't "merged" a nice way of saying that the men and children were likely murdered and the women taken for breeding? "Merged" conjures an image of living peacefully side by side and interbreeding for many generations.
That seems to be what happened with Neanderthals, at least at first.
Incidentally any violence may have been from the Neanderthals because almost all of the genetic data shows Neanderthal ancestry from Neanderthal males and homo sapiens females, and not the other way around.
Even when this did happen[1], the record seems to show trickles of gene-flow from these populations entering a much larger stream of genes from a more recently out-of-Africa population.
[1] And in a big complex world, it certainly would have happened sometimes.