Incompetence should never be accepted as an excuse, especially in a professional context where they should know better.

If someone injures me on purpose, or injures me due to incompetence, the net effect is the same. I am injured.

It's the same as "insanity defense" as an excuse for putting violent criminals back on the street. If they're so crazy that they don't know what they're doing, they belong in prison or a secure mental hospital.