Again, you err.
Here is a sampling of the analysis of 1 Cor. 15:29 by various biblical scholars/theologians wherein they recognize vicarious posthumous baptisms were being performed by early Christians in Corinth:
“The normal reading of the text is that some Corinthians are being baptized, apparently vicariously, in behalf of some people who have already died. It would be fair to add that this reading is such a plain understanding of the Greek text that no one would ever have imagined the various alternatives were it not for the difficulties involved.’’(Gordon Fee, The First Epistle to the Corinthians, Grand Rapids, Mich.: Eerdmans, 1989, pp. 763-64.)
“Again, the Apostle alludes to a practice of the Corinthian community as evidence for a Christian faith in the resurrection of the dead. It seems that in Corinth some Christians would undergo baptism in the name of their deceased non-Christian relatives and friends, hoping that this vicarious baptism might assure them a share in the redemption of Christ.’’ (From The Jerome Biblical Commentary, ed. Raymond E. Brown, Joseph A. Fitzmyer, and Roland E. Murphy, Englewood Cliffs, N.J.: Prentice-Hall, 1968, 2:273.)
“St. Paul then, almost in parenthesis, touches on what appears to have been a custom among the Corinthian Christians of baptizing by proxy on behalf of some, presumably members of the same family, who had died unbaptized and might therefore, it was thought, miss their chance of being incorporated into the fulness of Christ’s Kingdom at his Advent. This practice, says the apostle, makes as little sense as his own daily contempt for physical death, if there is no resurrection.” (William Neil, One Volume Commentary On The Bible, London: Hodder and Stoughton, 1973, p. 461)
“. . . the most natural meaning of the expression [used by Paul in 1 Cor. 15:29] is that some early believers got themselves baptized on behalf of friends of theirs who had died without receiving that sacrament.” (Leon Morris, The First Epistle of Paul to the Corinthians, London: Tyndale Press, 1964, p. 218)
“Close inspection of the language of the reference makes all attempts to soften or eliminate its literal meaning unsuccessful. An endeavor to understand the dead as persons who are “dead in sin” does not really help; for the condition offered, if the dead are not being raised at all, makes it clear that the apostle is writing about persons who are physically dead. It appears that under the pressure of concern for the eternal destiny of dead relatives or friends some people in the church were undergoing baptism on their behalf in the belief that this would enable the dead to receive the benefits of Christ’s salvation.” (James Moulten and George Milligan, The Vocabulary of the Greek New Testament, Grand Rapids, Michigan: Eerdmans Publishing Co., 1981, p. 651, original emphasis)
“Here Paul returns to his argument for the resurrection of the dead. There is a special difficulty in understanding v. 29 because we do not know the background of the words “baptized for the dead.” There are many interpretations, but it is difficult to find a satisfactory one. The present tense “baptize” suggests that the practice of baptizing for the dead was current and evidently well known to the Corinthians. . . .
. . . its [”huper’s”, the Greek word behind “for” in “baptized for the dead”] basic meaning with the genitive is “for,” “in behalf of,” or “in the place of.”
According to [H. A. W.] Meyer, this verse means that believers already baptized were rebaptized for the benefit of believers who had died unbaptized. This was done on the assumption that it would count for the unbaptized dead and thereby assure their resurrection along with the baptized, living believers. . . .(The Expositor’s Bible Commentary, Grand Rapids, Michigan: Zondervan Publishing House, 1976, vol. 10, pp. 287-288)
“. . . whatever doubt some members of the Church had concerning it, there were others who were such firm believers in the resurrection that they submitted to this rite of vicarious baptism on behalf of certain of their brethren, probably catechumens, who had passed away before they had been baptized and received into full membership of the Church.” (The Interpreter’s Bible, New York: The Abingdon Press, 1952-1957, vol. 10, p. 240)
Among these various scholars and theologians, there is little dispute that vicarious posthumous baptism was a practice of early Christianity.
I am aware of the various interpretation, but the CONTEXT does not support that. I Cor talks about the Resurrection. Paul uses “ they” not “we” (which he uses when talking about believers). What you posted is older views on it. Newer scholarship (especially Christian scholarship) equates it with a gnostic practice, not part of the orthodox Christian Church.
In either case, Paul does not condone the practice, he states that it occurs.
Yet the LDS draw this one sentence out into a whole system of temple rites.
This guy can explain it better than me:
http://www.hotm.tv/shows/20080909.htm
http://www.hotm.tv/shows/20061128.htm
Surely by now he stinketh.