If nobody believed in superstition it would be unable to hurt anyone


Miracles wreck your confidence in other people

A miracle is a magical event. For example, if a stone turns into bread then that is a miracle. Religion pretends that miracles are done by God as evidence of his presence and love.

Miracles cause judgement. If an atheist does not get visions to help (not force) or make him see that God’s word is true, the believer will have to grant the possibility that God doesn’t bother sending him visions for he is too stubborn to listen even to them. Christians may say they don’t assume that. But there is still a bit of judging there. They still say it’s a possibility. So that is a bit of judgement. Miracles lead to people becoming more judgmental in that sense.
The following is not an argument that a witness to a miracle is lying that it happened but that miracle beliefs make us unsure of what it was they were lying about.

If somebody makes a miracle claim, you can suspect fraud or a mistake. But showing something is supernatural is happening does not eliminate fraud altogether. For example, if you prove that Padre Pio really had miraculous stigmata, you cannot prove that he really suffered from these wounds though he said he did. Perhaps he used supernatural power to fake suffering. The supernatural explanation opens up a whole new dimension in terms of the person's honesty. It entitles you to find more things to be suspicious about than you would on the natural level. The interpretation of an event as miraculous violates the rule: any faith should not create unnecessary suffering or inconvenience for people matter more than faith. It should not imply that such treatment is valid.
Suppose miracles are signs from Heaven indicating the truth of God. By revealing through miracles, God is undermining unbelievers. Unbelievers are either liars or mistaken or both. But the fact remains that if we are going to believe in religion, we must limit ourselves to harmless beliefs - beliefs that bring no bother to anybody should they prove to be wrong. Unbelievers would have the right to be alarmed and feel threatened by reported miracles and their followers.