Baha'i teachings are absolutely wrong from a Christian pov. They base this on the infallible Word of God, their version of the Bible.
If the Baha'is are right, then Christianity not only never had the infallible truth, they've been deceiving people for 2000 years. Just the big ones, Jesus is God? No. Jesus rose bodily from the dead? No. Satan is real? No.
But how did Christians come up with these things? Their infallible Bible. But Baha'is can't say the Bible is infallible, because they believe there's errors in it... Like Ishmael, not Issac, being taken by Abraham to be sacrificed.
But the main error Baha'is point out, is to them, Christians misinterpreted their Bible. So for Baha'is, both the Bible and the Christian interpretation of it are not infallible, but wrong. So that leaves only one infallible word of God, the Baha'i writings.
So who's right? Two religions using their infallible word of God to show the errors of the other.