I believe you are saying when God speaks to Jews He is right but when He speaks to Christians He is wrong.
That is such a good point. But, which came first? The so-called OT. Did God write it or man? For a Christian, they have to say, "God" don't they? But then, who wrote the NT? God inspired people? Well let's see? Does it match up with the only "God's Word" they had at the time... the Jewish Scriptures. I can see why, many reasons why, a Jew would not accept the NT as being from God. However, after Christians made the letters from Paul and the others, along with the "gospels" the latest and newest Word of God... kind of like version 2.0 of God's Word, then I can see why Christians believe what they do. The new updates replaced the old version. Like the parable says... You don't put old software into new computers.
So was the old software wrong? No, just old and slow and not very easy to work with. The new software is so user friendly... believe and go. No page after page of useless commands to do. But some people are old school. They're dinosaurs and don't want to change... until the new system proves itself. So are there "bugs" in the new system? Yes, there's a lot of bugs.
So when people checked the OT, and it says not to do something but the new system, the NT, says "yes, do it"? What do you do? Both can't be right? Either the old system of beliefs is right. Or the new system has to show why the old one was "right" for then, but not for now.
Does the new system work? Can 1000 sects and denominations be wrong? Yes, I mean No, it does work... in a way. Especially when you upgrade to version 7.0... the new improved version of Christian beliefs. And they say God is the same yesterday, today and forever? He doesn't even have the same commands from millennium to the next. Sure dump the Laws, but tell me what "commands" do I need to believe and follow as a Christian? Call me when you get it all figured out. Or, better yet, send a pop-up when updates are available. You know, isn't that what the Jews did? They clicked on the updates from God, and read the terms and conditions of Christianity. Hmmm? Jesus is the Messiah, Jesus is God, no more Law, etc, etc? Then, after reading the terms and conditions, they clicked "Don't agree".