The criteria would likely be something like this.
1. Was what the other player did legal?
2. Could the other player's actions be reasonably viewed as unintentional?
3. Is the severity of the other player's actions worthy of some type of retaliation?
4. Considering the likely consequences of retaliating, is it worth it to do so?
My "default" interpretation setting is typically on "unintentional" (i.e., innocent until proven guilty), but it's really not that hard to make a judgement on that in cases in which the severity of the action warrants retaliation.