If the ignore list was set to a maximum of let's say 50 people, and only 10 changes could be made per week. Because there are so many people playing as a pirate, ignoring 50 of them would be almost meaningless, forcing people to only use the ignore list the way it should be used: to ignore disrespectful players (aka people who act like 10 year old brats).
The purpose of ignore lists is to tell the game that you don't want to play with, not even talk or listen to a particular player. The very attempt of discriminating between legitimate and illegitimate reasons for making that decision is foolish at best, because there will always be grey areas where there can't be any decision but a personal one. A sentence uttered would be interpreted as an insult or hate speech by one person, as harmless stupidity by another. An act might be considered as griefing by one person, as proper gameplay by another. You cannot dictate how someone should feel about another player, not because that would be inhumane (which it would be) but because it is simply impossible.
In other news, you underestimate the number of humans behaving like 10 year old brats throughout their entire life by several orders of magnitude.