Your question brings to mind a line I just read in William Barclay’s commentary on First and Second Corinthians. At the close of his chapter on 1 Corinthians 14:1-19 he writes:

‍“In the end only what satisfies my mind can comfort my heart, and only what my mind can grasp can bring strength to my life.”

‍The Corinthians had come to think speaking in tongues was more valuable than simple preaching. They thought that things which cannot be understood were better than the things that can. Paul said otherwise, reminding them that building up brothers and sisters in Christ takes priority — and only simple, intelligible preaching accomplished that. Here Barclay draws an important lesson: the mind must first understand a thing before satisfaction, comfort, and strength can be had from it. This sequence, I think, will help answer your question.

For we must first ask whether the doctrine of eternal punishment can be understood. From a purely intellectual standpoint, it cannot. The doctrine involves a contradiction, along the lines of a square circle or a married bachelor. It calls the opposed ideas of finite and infinite equal. It asks us to accept that the numerable sins of our lives, no matter how terrible, somehow equal and merit innumerable tortures. No mind can make sense of this because no mind can make sense of a contradiction. Here, at the outset, we face a logical impossibility, an insuperable difficulty, which no mind can ever understand.

But let us suppose it could be understood, for argument’s sake. Does the doctrine satisfy the mind? Does it satisfy our need for justice as its proponents argue? Certainly not — because justice carries with it the idea of proportionality. The punishment must fit the crime, we say. And it is for this reason that we oppose the death penalty for traffic tickets and recoil in horror at stories of disproportionate punishment — like, for example, stories of children having their limbs cut off for the crime of petty theft. Yet, by stretching punishment on to infinity, disproportionality becomes the centerpiece of the doctrine. Injustice increases; justice decreases. And because our moral intuition revolts against such disproportionality, our sense of justice is left unsatisfied.

Despite these heavy objections, proponents of eternal punishment might argue that the Bible teaches it. “And,” they may say, “no matter how obscure and difficult the doctrine is for our minds, teaching it will strengthen and comfort our hearts in some unknown way.”

But how, I ask? How does it comfort and strengthen our hearts to learn millions or billions of souls, some of them friends and family, will be tortured forever? How does it uplift any community to believe this? How does it help to know God allows this?

The fact is Jesus teaches the exact opposite of this doctrine. Jesus teaches that the holiness and justice of God consist in forgiving our enemies, not punishing them forever. Jesus tells us to turn the other cheek when we are wronged, to willingly suffer injustice at the hands of unjust men, to bless those who curse us. Why? Because it will make us like God. ‘You therefore must be perfect, as your heavenly Father is perfect.’ God cannot impose eternal and unrelenting agony upon His enemies because His very nature is love and mercy and forgiveness. Rather, God will make His enemies His friends. This is the strength of God and the comfort He gives.

So, to answer your question, I do think teaching eternal punishment has a negative impact. The damage is a mind left in utter confusion, the kind of confusion that says black is white or up is down. It leaves our desire for justice unsatisfied while increasing our feelings of injustice. It produces no comfort or strength of spirit. And, most importantly, it undercuts the teachings of Jesus and maligns the character of God. The simple, uplifting, and encouraging truth is that God is merciful, and any punishment given by Him is proportional, beneficial, and for the future reconciliation of the sinner. Only on this view, that of Christian Universalism, can each mind be satisfied and each heart comforted. The fact that we can believe anything else of a perfect God is testament to our fallen nature.