@Didymos Thomas,
There were responses to the original question, yes, but I saw no attempt to justify the scripture, just attempts to deflect responsibility for claiming to believe the scriptures by ignoring those scriptures that cast the original doubt into the mind of the person who started the thread. And it is a doubt that is shared by many.
As for the message being for everyone, I could quote another scripture, "Many have been called, few have been chosen." Yes, the message is for everyone, but that doesn't mean that everyone is meant to understand it.
Dirt and stone and air and water and trees and animals, and so on and so forth, also comprise the world. There's nothing in the verse that signifies that God was making a distinction, nor that he wasn't making one.
As you say, in the OT the term was "God's chosen people". Do we assume that because of the New Testament God no longer chooses who is or isn't his child? If so, then let me remind you about the "few have been chosen" part. That's from the New Testament. If it doesn't make you different from others to be God's child, then why call yourself Christian? Why bother with a label, a distinction?
For me, what I am doesn't make me better than anyone else, but it certainly makes me different. It can't possibly make me better, because I had nothing to do with becoming what I am. God made the decision, not me.
Where this originally pure intention went remarkable awry was when people started thinking that they had something to do with their own salvation. Christianity began to teach that your actions make you a Christian, so that those who perceived themselves as doing those actions began to think that they accomplished something that other, shall we say, less capable human beings did not/could not accomplish. Thus pride entered the equation and the result became something unbecoming.