Which is a fallacy argument. The only way that argument could be valid is if Mercenary and Soldiers had everything in common, which they don't.
They do, in regards to the specific point I am refuting here, which I have proven false.
You claim that "The **act** of volunteering to risk life and limb for others over an extended period of time is worthy of respect" I point out that mercenaries on extended missions risk life and limb for others over an extended period of time. I also hold that mercenaries are not worthy of respect, and therefore soldiers are not inherently worthy of respect (which is itself an absolutely ridiculous claim). I make no claim for a relationship between mercenaries and soldiers here outside of that particular point.
Here is a second bit of wisdom that the WW2 paratrooper taught me as a child: "Don't confuse the people who fight wars with the people who start wars. They are not the same people. Soldiers don't get to choose what wars they will fight, what Presidents they will trust."
I won't disagree, but that makes them parties that make sacrifices, not heroes.
One of the few privileges that a U.S. soldier has is to refuse to commit a horrific crime. Save the hyperbole for political rants.
No, they have the right to refuse to commit a subset of horrific crimes specified in the Geneva convention. War itself is horrific by its very nature and is at least a necessary evil. Even at a basic human level, healthy people have problems dealing with it, which is why strict deference to authority and dehumanization of opposing forces are such common tactics, often accompanied by some lofty claimed goal that likely masks the more banal reasons that a leader wants to throw bodies at an issue instead of negotiate.
Other mercenaries who probably also lack confidence in the mission and/or the leadership and after re-calculating the risk/reward see breaking the contract as the best outcome.
It would depend very much on the particular context. I would consider hitmen employed by the mafia to be mercenaries, but they can't easily turn their back on a contrct.