The elder is not to deviate from the message he was taught. If this letter is not a fake, the message is none other than Paul's message. There were no Christian scriptures at the time. The message came by word of mouth. There doesn't appear to be any epistle to the Cretans. It is considered trustworthy by Paul if it originated from him. His doctrine is the only sound doctrine. Since Paul addresses those who would oppose it, it is certain that there were already persons opposing it.
Paul died before the destruction of the temple in 70 CE, probably in the 60's. So, in the thirty years between Jesus's death and Paul's, minus fourteen years in the wilderness. Paul probably travelled and preached his message approximately 15 years. In that time, he came to expect his teachings about Jesus to be the standard. The "gospels" of Matthew, Mark, Luke and John, most likely came later. It is possible Mark was produced during Paul's lifetime, but there is no indication Paul heard of it or read it. If he did, he may have even regarded it as a false gospel.
Who would oppose Paul's gospel of salvation and spiritual equality for the gentiles? Obviously Jews. I imagine Yahweh believing gentiles would have been his easiest targets. Those who profited by the pagan traditions would also have been offended. Verse 10 goes on to say "There are many rebellious people, mere talkers and deceivers, especially among the circumcision group." AKA Jews. Yep. Verse 11: "They must be silenced (???), because they are ruining whole households by teaching what they ought not to teach-- for the sake of dishonest gain." The dishonest gain is not elaborated on. Perhaps local Jews charged fees for the circumcision of converting gentiles? Who knows.
Verse 12-13 says, "Even one of their own prophets has said, 'Cretans are always liars, evil brutes, lazy gluttons.' This testimony is true. Therefore, rebuke them sharply, so that they will be sound in the faith and pay no attention to Jewish myths (???) or to the commands of those who reject the truth." (Did Paul completely reject the whole Jewish mythos now contained in the Old Testament?) Read about the Cretan Epimenides and his statement about Cretans here. The statement is often considered a paradox because Epimenides was a Cretan himself, which would make him a liar. However, the statement originally occurred in the context of a poem:
"They fashioned a tomb for thee, O holy and high one
The Cretans, always liars, evil beasts, idle bellies!
But thou art not dead: thou livest and abidest forever,
For in thee we live and move and have our being.
The Cretans, always liars, evil beasts, idle bellies!
But thou art not dead: thou livest and abidest forever,
For in thee we live and move and have our being.
I wonder if Paul knew he was quoting a poem about the immortality of Zeus? The fourth line of this poem also occurs in Acts 17:28. There, Paul tells the Athenians it was from one of their own poets, He appears to be either referring to Yahweh, or equating Yahweh with Zeus. That would be interesting.
At any rate, the phrase as it appears in Titus is downright insulting of the Cretans, the very people whom Paul wants to be good little Paulites, um, Christians.