No,scripture does not state they are picked out of Christian people's.I re read your post. You don't say what you think the purpose is for the 144k.
The word translated 'redeemed' in Rev 14:3, is 'ransomed' in the REBible. Jesus stands on Mt Zion and selects them out of the vast multitude of Christian peoples. Rev 7:1-10
I proved that their task is to go out to all the world and proclaim the Gospel of the coming Kingdom. Isaiah 66:19
As for frustration caused by misunderstandings, I get that; plenty, as people like you have fixed beliefs about Bible Prophecy and for me to show where they are wrong, causes upset.
Also you have not proved where they proclaim of the coming kingdom.
You simply do not comprehend scripture or don't know it. To hats why you assumed I said they were the removed from the earth when in fact I had quoted me scripture that you were unfamiliar with.It was you ignorance of scripture to what caused the misunderstanding.
Thats why I had to find the verses for you that you did not know and quote them for you and I had even boldened it for you.