NuclearPenguins said:
Kilrathi place honor as the highest of their values, so if was to be dishonored it is naturally expected that they would either commit ritual suicide to prevent their family's name from going down with them, or the entire family would have to become rogue. As outcasts they would have to resort to pirating to survive, as they couldn't live anywhere near where the other clans would have power.
I agree that Kilrathi pirates could form the core of some of the pirates. However there could also be another explanation.
If we look at our own history we find one empire that is very similar to the Kilrathi empire; The Japanese Empire prior and during the second World war. For a japanese soldier, surrender was the most dishonorable thing to do. You fought and died for your empire, nothing else.
Since the japanese had been indoctrinated with this thinking from the day they were born they became fanatical fighters (just ask the veterans in the allied navies about the Japanese Kamikaze's).
When WWII ended the commander of the U.S. Pacific fleet sent a message to his japanese counterpart. That message ended with:
"Although we today sign the cessation of hostilites there might be some kamikazes who will make some last desperate attemps to attack us. If so, they will be shot down in a friendly manner"
I haven't read anything about desperate last attacks by kamikaze's after the end of hostilities in the historybook, but the fact that the U.S. Commander didn't ruled that out shows how fanatical the japanese soldiers must have been.
Looking at the Kilrathis, they have the same kind of indoctrination as the japanese. Honor is the most valued asset, to a Kilrathi there is only honor if a warrior is either victorius or dying bravely in combat.
As there probably were japanese who saw Japan's surrender as a betrayal there is probably many Kilrathis with the same feeling.
To make long story short, Kilrathi pirates could be dishonored Kilrathis with no other way of living and/or Kilrathis who sees the Kilrathi empires surrender as a betrayal and therefore refuses to aknowledge it and continues on the fight.
One such example is the novel "False Colors" by William R Fortschen in which a renegade Kilrathi warlord wants to start his own crusade against the federation
Mvh!
T-rex