I agree. The bible does not contradict itself. The word eternal should be enough for believers. Eternal is eternal. Nothing conditional about that at all.
A believer would never be called a false teacher as is described in 2 Peter 2. Those with the truth preach the truth. False teachers bring in these heresies because they are in darkness. Heresies would be teachings that add to the truth, as a substitute for truth, inconsistent with the revealed truth of God. What true believer would ever add to the scriptures?!
Galatians 2:4: "...And this occurred because of false brethren secretly brought in (who came in by stealth to spy out our liberty which we have in Christ Jesus, that they might bring us into bondage)"
2 Peter 2:1-3: "But there were also false prophets among the people, even as there will be false teachers among you, who will secretly bring in destructive heresies, even denying the Lord who bought them, and bring on themselves swift destruction. And many will follow their destructive ways, because of whom the way of truth will be blasphemed. By covetousness they will exploit you with deceptive words; for a long time their judgment has not been idle, and their destruction does not slumber"