Here are a couple potential harms from urban legends:
• Spread of misinformation. Urban legends are false stories that become widespread, but they are presented as factual tales of things that supposedly really happened. The spread of these false stories can confuse people and undermine the truth.
• Anxiety and fearmongering. Some urban legends prey on common fears and anxieties to captivate audiences. Stories about things like poisoned Halloween candy, killer alligators in sewers, or teens dying after prank calls can stoke unnecessary fear and paranoia.
• Moral panic. Occasionally, an urban legend will capture people's imaginations and stir up a kind of moral panic. Things like the supposed "Satanic panic" of the 1980s, rumors of ritual animal sacrifice, or claims of gang initiations gone wrong can lead to panic and hysteria that is disproportionate to the facts.
• Blame and harm. Rarely, an urban legend may single out a specific group for blame or paint them as a threat, fueling hostility toward them. For example, stories of minorities spiking Halloween candy or teens dying after prank calling certain number combinations can promote blame of marginalized groups. This type of narrative can conceivably inspire real-world harm.
• Distraction from truth. The spread of emotive and shocking urban legends can distract from and crowd out coverage of legitimate news stories and important truths. They serve as sensationalistic clickbait, spreading misinformation.
Those are a few of the potential downsides of how urban legends can negatively impact beliefs, spread fear, lead to moral panic, promote blame, and distract from truth. Of course, most individual urban legends cause relatively little harm—but they are worth examining critically given these possibilities.