"Arrogance on the part of the meritorious is even more offensive to us than the arrogance of those without merit: for merit itself is offensive"

This quote recommends that conceit is undesirable, however when it comes from somebody who has actually achieved a great deal, it is much more offending. Nietzsche appears to suggest that those who demonstrate benefit might be excessively proud of their achievements, and this pride is specifically unpleasant to others. Additionally, Nietzsche asserts that merit itself is offensive, which might mean that he believes that striving for quality or success is naturally bothersome in some way.