What would you do?

I would confront him privately, ask him what he truly believes from Scripture, and sort it out from that angle.
You may have to part ways with him.

I would also, at the earliest possible point, correct ( or have corrected ) the error towards the affected congregation...letting them know that baptism does not save ( as the Churches of Christ and several others teach ).
Baptism is a command that the Lord made that symbolizes what He did for us.

"Buried in the likeness of His death, raised in the likeness of His resurrection to walk in newness of life" is how I was first introduced to it at the age of 12.
Scriptural references for this are:

"Therefore we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life." ( Romans 6:4 )

" Buried with him in baptism, wherein also ye are risen with [him] through the faith of the operation of God, who hath raised him from the dead." ( Colossians 2:12 )

I understand baptism to be symbolic, not only because of these passages, but because to understand it any other way is to ascribe an action or a ceremony to the God-given act of regeneration.
From my perspective, a misunderstanding of passages like Mark 16:16, Acts of the Apostles 2:38, Acts of the Apostles 22:16, and 1 Peter 3:21 leads to teachings like "baptismal regeneration".
Since becoming born again is by God's will and not man's ( John 1:13 ), then no physical act of man can "trigger" the process, like baptism.

To me, "Baptismal regeneration" also has a "side effect" in its teachings...it unintentionally ( or it could be intentional, depending on who you ask ) seeks to make eternal life into a reward instead of a gift, by performing an action to trigger the process of becoming born again.

My opinion?
It is a command to be followed, but has no spiritual implication...
In other words, a person can be born again, but fail to be baptized themselves in their own lifetimes.

Cases:

Abraham
Isaac
Jacob
David
Gideon
Samson
Samuel
Isaiah
Jeremiah

...and so on.

It is identification with who we are "in Christ", and nothing more.
What He did for us, but symbolizes and commemorates, with physical water, our being baptized spiritually with His Spirit and the "water" of His word ( Ephesians 5:26 ).

It is, however, important that we follow it, because He has commanded it under the new covenant.



God bless you, my friend.

 

No one is a perfect preacher except Christ. No one has a perfect doctrine. Perfection does not exist in this life.
MB