Add to that the fact that he chose not to avenge his son, and you may praise his dedication to peace all you want, but at the end of the day what the other dons saw was a weaker don, like Michael told him "a sign of weakness".
It WAS a sign of weakness but make no mistake about it ... Vito got to avenge his son's death (if only by planning the revenge). Revenge was everything to him... even if it meant waiting a long time. Vito bided his time, giving the Family much needed time to regroup and prove that he really wasn't weak at all.
