Are all non-Muslims damned

The claim is often reported honestly, because it is often what the reader was actually taught. The teaching was wrong, and correcting it matters more than defending whoever delivered it.

Judgment

No person is in a position to assign another to the Fire. Judgment belongs to God alone, and it has not been delegated to teachers, relatives, or writers. A person who issues that verdict over your friends has claimed an authority he does not possess.

The category

The operative term is kafir (one who rejects the truth). It is not a synonym for “non-Muslim”, and treating the two as interchangeable is the error on which the whole claim rests. Whether a specific person rejects a truth he has genuinely recognised is a matter of that person’s interior state, and it is not open to inspection by a stranger.

Qur’an 2:256 states that there is no compulsion in religion. Each person chooses from what lies before them, and each is judged justly. A doctrine of automatic collective damnation cannot be built on a text that establishes free choice.

What the tradition does hold

Islam accepts that Muslims themselves may be punished for their sins. The tradition does not offer its adherents an exemption, and any presentation of it as a membership card is a misrepresentation from inside the community as much as from outside it.

A teacher who told a child that her friends are damned taught her something the sources do not support. She is entitled to know that, and to stop carrying it.