You weren't stating it as a opinion. You said you are a bad staff member, don't lie. You never said "I think".
Then I asked you to quit saying it for like 15 times, you continued, which you shouldn't have done.

You weren't stating it as a opinion. You said you are a bad staff member, don't lie. You never said "I think". Then I asked you to quit saying it for like 15 times, you continued, which you shouldn't have done.