Oh, there's profit in war and peace. One just needs to be imaginative enough to figure out where it is and how to get it. There's a lot of money to be made and power to be gained in the "anti-war" profession. Perhaps as much in "war profiteering." But, like soldiers the demonstrators are not the one's reaping the monetary rewards.
Killing, legal and illegal is just the nature of man, no on/off switch. People kill for a number of logical reasons and illogical. We humans have a propensity for justifying killing each other, profit, convenience (aged parents, unwanted children), illegal passing (road rage), trespassing, mental problems (a subjective and social decision), politics, real or imagined wrongs of all types, it's all in the prospective of the killer. We kill legally in wartime and "peace", sometimes happily and gleefully, sometimes with hesitation and remorse and ... often under color of law.
We develop new words and laws (late term abortions, euthanasia for the aged or inconvenient/expensive to maintain). Situational ethics allow us to justify all kinds of killing and come up with new, subtle and often benign sounding words to describe simple killing. Such makes it easier for society to accept but, it's killing none the less.
The threat of mutual destruction is all that kept us in business during the cold war. Now we are threatened by certain societies who are not afraid of death, welcome it in fact. "Mutual assured destruction" will soon not be a safeguard once some of them become nuclear enabled. Then, the human race will indeed be seriously threatened.