We can be called children of God in more than one sense, not just through baptism. We can be called children of God because we are all made in His image and His likeness.
We seem to be looking at it from different perspectives. Yours is based on people being baptized, which isn’t incorrect. I’m not saying you are wrong theologically. I’m saying that if we don’t view others as children of God (made in His image and likeness) we risk viewing people negatively. During the crusades, Muslims were looked upon as “not children of God” which would make it easier to wage a crusade against them. If we say “they aren’t children of God” or if we don’t actively try to see Christ in our brothers and sisters, it is “easy” to view them negatively or with hostility. Pride becomes easy. Self entitlement becomes easy.
In no way am I saying baptism is unnecessary, because it is. I’m just saying, for me personally, it’s better to view others as children of God, so I don’t think of myself as better, holier, more worthy than them.