I don't think any of them are looking to be excused from their role - when innocents are killed, those responsible often carry those scars with them for life. The members of the military I know (active and retired) have worked tirelessly to accomplish their assigned missions and avoid unnecessary destruction and injury to innocents. For those that have been involved in such (and I know some), it is a guilt and burden that they will carry and have to deal with until they die.That does not excuse their part in the tens/hundreds of thousands of innocent civilian deaths as a direct result of the US war on terror. I am not too sure what their "good intentions" are but any reasonable person would think twice about taking part.
For many young men and women, armed services are a "way out" as others have said - for others, it is a calling to serve their country. Regardless, when they come together, they frequently do "heroic" things. The first that they do, frankly, is that they have voluntarily chosen to go in harm's way if ordered to do so - and that applies to every single one of them, from cook to SEAL, from fighter pilot to tank mechanic.
Also, @steveojcc identifies correctly that we need to do a much better job for our veterans - he is absolutely right.