Accountability can respect someone’s dignity while refusing their excuse.

You can take someone seriously as a person and still decline their explanation. The two are often treated as a package, so that rejecting the excuse feels like an attack on their character and accepting the person seems to require accepting their account. Holding them capable of having chosen differently is itself a form of respect, and it is the opposite of contempt.

When someone offers a reason that does not hold, say so without commentary on who they are. Name the behavior, name what you expected, and leave their worth out of it entirely. Most people can take a clear no about an action far better than a vague disappointment about themselves.