This is from TV Tropes's Teleporter Accident page:
An old sci-fi story dealt with aliens coming to Earth and offering to share their technology with humanity, including teleportation. Unfortunately, the alien civilization is stagnant, and has been for centuries ever since the discovery of the teleporter, as the alien interacting with humans and studying their 'quaint' beliefs in souls and psionics learns that souls do exist and anyone who's been run through a teleporter loses his soul and all that's left is a soulless shell. Without souls all development and creativity had stopped for them and to save humanity from that (apparently he was unwilling or didn't believe his people would believe the truth) the alien destroys his ship and all records in their database referencing Earth. It ends with a reporter detailing the story and sadly thinking how he'll never again create anything new, as he was part of the group of humans run through the teleporters to show that they were safe.
Does anyone happen to know the name of this story? I'll accept the best match.