Baptism is not the only form that appeals to the Father can take. And the thief is a prime illustration of that. I just posted a half dozen verses to you talking about salvation and they either don't mention baptism or it's performed after what the verses says is necessary for salvation.
Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost: Teaching them to observe all things whatsoever I have commanded you: and, lo, I am with you always, even unto the end of the world.
Jesus did command us to baptize and I don't dispute that. He also told us to observe all things whatsoever I have commanded you. Well He commanded a tremendous amount of things. Is it your contention that failure to do all that Jesus commanded voids salvation or that salvation is contingent or not conferred until after all things He commanded are done? Of course not, so why are you twisting this verse to make it something it's not. It's a command to baptize, but it doesn't make water baptism necessary for salvation. Jesus said many times that belief in Him was what was necessary for salvation and that all that believed in Him would have eternal life.
Water Baptism is important, but it is not critical to salvation. Only faith that generates an appeal is necessary.
Well, yes, obviously, if the failure is culpable and not repented of.
"Why do you call me, `Lord, Lord,' but you do not do as I command?" It's a command to baptize, but it doesn't make water baptism necessary for salvation.
Are you going to explain to Jesus on the Last Day which of his commands were optional, and which weren't?