If you wish, I will tell you how he breaks down your own foundations. No problem.
First, I did not tell you that Jews hate Welhausen. They don't agree with him. That does not mean hate. I am surprised that you would even drop his name if you don't know his thesis.
Welhausens source criticism brings a different paradigm for the Jews. Of course. It breaks down their belief in the Mosaic tradition. The Y source (J source) and the Elohists (I try not to pronounce their God's name) make a source basis for God's name. That falsifies God has a name. And the D will make it a new source, not mosaic. P source makes it strategic, not revelation.
Why would this break down your premises? Because it takes the authenticity out of the writings. Each source have their own agenda. So how would you authenticate it as true, false, genuine, historic or even apt to the time period in question? This completely breaks down your readings from the Pentateuch which is where you take your sources from.
I actually don't know why you dropped Welhausens name in this thread. It's irrelevant to that post you replied to, and it's irrelevant to this thread, it's also irrelevant to the Jews because they will never take his scholarship for linguistics, hermeneutics or interpretation. One main reason would be because Welhausen does not engage in any of these things.