They understand, they just don't care and shouldn't care. It is always jarring to encounter someone with a different life experience, but processing that is your business. They don't need to spend the rest of their life crafting their words to avoid making people uncomfortable.

It's the same principle as someone in public when they're disfigured. You just became aware of something traumatic that happened to this person, and it is totally understandable to feel uncomfortable. But they are just existing in public. They have no obligation to present themselves in a way that avoids making you uncomfortable, and doing that everyday of their lives would be exhausting and wasteful.

In that example it is immediately obvious that it would be inappropriate to ask them to cover up. But it's the same principle, either way.