The frustration-aggression hypothesis is related to Libya in that it can be used to explain why the rebels were so aggressive towards Gadaffi when he was captured.
This hypothesis holds that aggression happens when people are frustrated in their desire to obtain something. In the case of Libya, Gadaffi had been frustrating people's desire for freedom for decades. Because of this, the hypothesis would argue, the people became very aggressive. In this case, they were able to actually confront the source of their frustration. This made it very likely that aggression would result.
In the case of Libya, then, the rebels became very aggressive towards Gadaffi because he had frustrated their desire for freedom.