Just a perfunctory glimpse at history will reveal the fact that the Declaration and the Constitution were written under two divergent legal standards. What kind of question is this?
I don't care. Point is that the Pledge, as it stands now before under God is taken out, is not in violation of the first amendment because it's not a law respecting or establishing a state religion. The word God meant many things to our founding fathers and I suspect means many things to us today. It doesn't say "one nation under Jesus Christ," or etc. One also has the option of skipping the words and I'd also point out that in the Pledge, one is not swearing allegiance to God or a god, so it's not in violation of the first amendment. Other than spout the usual jargon about how we'd all be better off we saw the world through your enlightened lenses, you have failed to argue otherwise.
What I'd say is what about everyone else's rights? Ever hear that the needs of the many outweigh the needs of the few? The US Congress voted a decisive vote of support for the Pledge as it is now and the vast majority wants under God to remain in the Pledge, so if somebody is offended, tough.