So basically what you're saying is that exercising sound ethical judgement is a bad thing
I think it's pretty clear that is not what I am saying.
you consider it respectable for a person to sign up to take part in an oppressive foreign occupation because their motive may be to "protect us?"
Yes. If their motivation for signing up is to "protect us", then I have a great deal of respect for them. My respect for people willing to give their lives to serve others is not dependent on whether or not the services they provide do us good.
Consider the following scenario. Alice is crossing the street right as an oncoming bus approaches. Bob sees this, jumps in the middle of the road, and pushes Alice out of the way.
Whether or not the bus stops (meaning whether or not Alice was in any real danger). If Bob's intention was to give up his life to save Alice's, then I would have respect for him.
In real life, it's actions that matter, not words.