Yes, there is an "idea", a concept of a God and people are told it is real and to believe in it and to pray and worship it. But are those "ideas" and concepts all the same? No. If they are all different, can they all be real? Do any of them have to be real? To accomplish their purpose, I don't think they have to be real.
A religious leader or prophet says, "The Great Being in the Sky has spoken. He wants us to worship and praise him and build him a temple. He has given us these laws to live by and says that he wants you to give him 10% of your earnings to him. He has entrusted me to be the keeper of all that is collected until which time he comes to get them."
How many religions do that or something similar? An invisible God that only the prophets can speak to... that gives the people laws and has the people give him offerings or sacrifices?
For me the simplest explanation is still that each people and culture created their own Gods and religion to suit them. Compared to some other religion in some other culture, it's probably going to be different. And what do we see? We see those differences.
One explanation used by some religions is that they are the one true religion that believes in the one true God... all the others are false and those Gods aren't real.
Some religions say that one or more of the other religions are true but then have gotten a few things wrong. So, their prophet was sent by God to correct those misunderstandings.
Baha'is are the extreme of that. They say that most all the religions were true and the only reason there are "apparent" contradictions is because the people misinterpreted things and added in some of their own ideas into the original teachings of the religion.
For Baha'is that settles the confusion. The claim is that "originally" all the prophets came with a true and pure message from the one true God. Then people messed it up. Naturally, it is the Baha'is that tell us what is true and false about those other religions.
So, for a Baha'i, since they believe there is only one true God, then all these old religions must have come from that one true God. Just because people describe that God a little different and call him by another name, that doesn't mean it's a different God. Sure, great for Baha'is... But does the reality of what we see in the beliefs of the different religions support it?
Why not discuss it and debate it? As we know, that's not a Baha'i strength. They are good at claiming things... just not so good at showing evidence that supports their claims.
Again, the intent of LH is to get us all to love each other and accept each other's beliefs as true. Why fight and quibble over beliefs? But, ultimately, the only true belief, because it is the newest and the only one that hasn't been messed up by people, is theirs, the Baha'i Faith. It is the only one that has the truth needed for today. Or so they say.
Okay, let's discuss it. Let's debate about it. Oh yeah, we've been trying to do that. And they've already told us. They are right, because Baha'u'llah said so. And what he said came from the all-knowing, invisible God that we can believe is real. Why? Because he said so.
So, it all hinges on whether or not Baha'u'llah is who he says he is. Okay, let's discuss... No, no. No discussing. No debate. It is clear and evident he is God's prophet. Why? Because his mission, his character, his writings. I know that's such "solid" evidence, but can we discuss and debate about that just a little?