Is it dangerous to substitute unit tests for user testing? [closed]

Question

Is it dangerous to substitute unit tests for user testing?

A co-worker believes we can reduce the manual user testing we need to do by adding more unit tests. Is this dangerous?

Unit tests seem to have a very different purpose than user testing. Aren't unit tests to inform design and allow breaking changes to be caught early? Isn't that fundamentally different than determining if an aspect of the system is correct as a whole of the system? Is this a case of substituting apples for oranges?