It doesn't get any more Scriptural than Matt 28:19. That's what we do.
Well, if that's truely what the Catholic church does then God will be pleased. Mark 16 gives us another look at that verse in Matthew...
Mark 16:15 And he said unto them, Go ye into all the world, and preach the gospel to every creature.
What is the gospel?
According to BlueletterBible it comes from
euaggelion which basically means salvation through Christ.
This would be echoed in verses like...
Acts 4:12 Neither is there salvation in any other: for there is none other name under heaven given among men, whereby we must be saved.
However there are 'other gospels' that people preach.
Galations 1:8 But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed.
So preaching 'another gospel' is pretty seriously bad.
What would be 'another gospel'?
I believe anything that teaches in salvation through anyone other then Jesus. I believe the following are examples of 'other gospels':
--"Taken up to heaven she (Mary) did not lay aside this saving office but by her manifold intercession continues to bring us the gifts of eternal salvation..." Pg. 252, #969
--"The Second Vatican Council's Decree on Ecumenism explains: 'For it is through Christ's Catholic Church alone, which is the universal help toward salvation, that the fullness of the means of salvation can be obtained.'" Pg. 215, #816
--"The Church affirms that for believers the sacraments of the New Covenant are necessary for salvation." Pg. 292, #1129
--"The Church does not know of any other means other than Baptism that assures entry into eternal beatitude..." Pg. 320, #1257
Just to point out, Scubie.... you've spent quite a lot of time arguing in a mode of "my Scripture verses" vs. "your Scripture verses."
And the fact is, in most cases it's easy to find verses in one place or another that support either of the positions in this argument.
That should give you serious pause. Perhaps, just perhaps, things are not nearly so cut and dried as you want them to be. And once you realize that, perhaps you and yours will be less willing to condemn those with whom you disagree.