If a current or former imperial troop turns a traitor to the empire, then that is an undeniable win. There have been many cases in US history of its troops turning against and betraying their masters, and joining the anti-war movement, and helping other troops do so also. Every single troop that does so, means less innocent people harmed. This should be encouraged and applauded.
We should see people less as static entities and identities, and more as capable of change. All communist countries (PRC, USSR, Vietnam, Cuba) during their civil wars welcomed traitors who saw the wrongness of the other side to their cause with open arms.
I also doubt the claim that many of these former troops would want you to feel sorry for them. If they didn't think they did anything wrong, then they wouldn't have joined the anti-war movements in the first place.