Beloved, although I was very eager to write to you about our common salvation, I found it necessary to write appealing to you to contend for the faith that was once for all delivered to the saints. For certain people have crept in unnoticed who long ago were designated for this condemnation, ungodly people, who pervert the grace of our God into sensuality and deny our only Master and Lord, Jesus Christ.
2 John 9
Everyone who goes on ahead and does not abide in the teaching of Christ, does not have God. Whoever abides in the teaching has both the Father and the Son.
1 John 2:23-24
No one who denies the Son has the Father. Whoever confesses the Son has the Father also. Let what you heard from the beginning abide in you. If what you heard from the beginning abides in you, then you too will abide in the Son and in the Father.
2 Timothy 4:3-4
For the time is coming when people will not endure sound teaching, but having itching ears they will accumulate for themselves teachers to suit their own passions, and will turn away from listening to the truth and wander off into myths.
I'm not claiming that I know for sure. I just wrestle with what texts like these say to a pluralistic society.