Sir Launcelot of the Lake, though famous and noble, was not perfect and sometimes made mistakes or behaved improperly. The quote suggests that even the greatest heroes are fallible and prone to errors. No one can claim to be flawless or never to have erred at some point in their life.
The passage emphasizes that everyone, regardless of their stature or achievements, is susceptible to wrongdoing. It encourages humility by acknowledging human imperfection and recognizes that mistakes are part of the human experience, even for legendary figures like Sir Launcelot.