give this staircase that seem like a very reasonable fear

Looks like it might be SMART to be nervous about those stairs

So people with this fear live horrible lives so they don't have to go there?

By Toutatis... the sky always could fall in our heads... unless you use the shield... would say Astérix's chief Vitalstatistix

How would people pass each other there?

Xenophobia is a dislike or fear of people from other countries or of that which is foreign or strange.
Not sure how this fits the theme.