If you consider Mark 16:16 is part of the original gospel (and therefore Scripture) and wasn't added later, then be careful playing with snakes and drinking poison. Mark 16:18a, "they will pick up serpents with their hands; and if they drink any deadly poison, it will not hurt them;"It says exactly that.
Mark 16:16 ---> "Whoever believes and is baptized will be saved, but whoever does not believe will be condemned."
It looks like you and the other anti-Sacramentalists are trying to center the command on "believe" and make the point that if one doesn't believe the Gospel, he'll be condemned.
Guess what, no one disputes that!
But the teaching of Jesus in Mark 16.16 is NOT what is required to be damned, but what is required to be saved. The conclusion many of you are trying to reach-- which is that because not believing alone is sufficient to condemn, therefore believing alone is sufficient to be saved -- is both illogical, and false to the text.
First, our Blessed Lord describes two necessary conditions in the first clause: belief and baptism. In the second clause, He is describing a person who, by not believing, lacks the first essential condition. Ergo, that person will not be saved.
Second, why do you all seem to think that because Jesus doesn't mention baptism in the second clause, that He's taking back what He said about the need for baptism in the first clause? He was clearly understandable to the Apostles -- and to the entire Christian world except for a minority of Protestant dissenters -- to be saying that he who believes them when they preach the Gospel, and therefore believe their preaching of baptism for the remission of their sins (Act 2.38) -- and obey, will be saved. It's obvious that Jesus and His Apostles understood that no one who refused the Gospel was going to be baptized. Why would he?
Furthermore, you are being false to the text by attempting to use the second clause to nullify the first. Jesus already introduced belief as one of two necessary conditions for salvation in the first clause. Since the unbeliever in the second clause already lacks the one of the two essential conditions, there is no reason to even mention the second, which would be insufficient by itself. Why would there need to be a separate penalty for not being baptized or any other omission? The person who doesn't believe has already failed to meet one of the two necessary conditions that Jesus just laid down: belief and baptism. There is no logical need for an additional "penalty."
Are you and the other anti-Sacramentalists asking us to believe that Jesus' command in Mark 16.16 is His way of saying if you don't get baptized, God won't hold that against you? In other words, baptism is just a suggestion?
Even if you can't accept that is is clearly a non-Markan addition, consider what 16:16 says: "Whoever believes and is baptized will be saved, but whoever does not believe will be condemned." The emphasis is on belief. It doesn't matter if a person is baptized multiple times, if they don't believe that Jesus died for their sins and that they have a new life in Him, they are not saved.