I planned to slice in backend development into to the user stories vertically. But a backend guy on our team started to complain that this makes their work invisible.

My answer was that

• at the sprint planning and review meetings we discuss backend tasks in front of stakeholders so it makes it visible, and

• maintaining a high quality during the project will result a slower startin pace than other teams, but we will have a stable velocity during the project. And velocity is highly visible to stakeholders.

He still insist having stories like: "As a developer I need to have a domain layer so I can encapsulate business logic."

How can I solve the issue before it pollutes the team?

The root of the issue is that our management systematically consider backend work as invisible and call backed devs miners, or other pejorative terms.