The translation of this structure (marked in bold) and its corresponding example sentence are not accurate. You can't forgive something someone. A better translation of the sentence might be "forgives him FOR his eccentricities" or maybe simply "forgives his eccentricities"
|pardonner [qch] à [qqn] vtr + prép||(tolérer)||forgive [sb] [sth]⇒ vtr|
|put up with [sb]'s [sth] v expr|
|Le directeur lui pardonne ses excentricités car il est très compétent.|
|The manager forgives him his eccentricities because he is very competent.|