There are not 6 million Arabs in Judea and Samaria.
There is no demographic threat. This was a false canard raised by the leftists years ago in order to propagandize for the two-state solution, and it has been thoroughly debunked for years. See, for example, http://foreignpolicy.com/2013/12/18/israels-demographic-time-bomb-is-a-dud/ Nobody can accuse Foreign Policy magazine of being right wing, and even that publication admits that the demographic threat does not exist.
There may be realpolitik reasons why it would be difficult for Israel to annex Judea and Samaria, but Israel would face no internal threat as a result of doing so.
Yes, indeed ... if Israel took over all the land it conquered, it would get SIX MILLION ARABS.
As to what impact they would have, all you have to see, in that regard, is that RIGHT NOW, without Israel taking over all the land, the existing 20% of the Arabs already have the THIRD LARGEST PARTY in Israel. Add in those extra Arabs, and you don’t have a Jewish State any more, but an “Arab-controlled state”!
Don’t argue with someone who breathlessly uses ALL CAPS, and appears to think they know more about Israel than Jews. Ignore him/her.