If there is any one occupation that is categorically heroic, "soldier" probably comes closest to it. Essentially what a soldier does is give up their personal freedom to do tasks solely for the benefit of their country. They have no control over where they are sent, limitations are placed on their ability to speak in public, all of the liberties the civilian enjoys are severely curtailed. The only reason civilians have those liberties is because of soldiers in the past. Conscientious objection goes out the window. You cannot object to what your CO tells you like you can reject what your boss tells you (though its unwise to do so in their presence)
Jihadists are not soldiers. They do not fight for a nation. They claim to fight for a religion but the greatest number of victims actually share that religion. We wouldn't have so many of what Ancien Regime calls "mass murders" if our enemy didn't view maximizing collateral damage and civilian deaths as a strategic necessity.
There's also the usual stunning display of ignorance about what the military actually does. Yes, soldiers are trained in armed combat and expected to be able to kill any target with maximum efficiency. That is not the only job a soldier though. Part of the military strategy in Iraq and Afghanistan is working with the locals to rebuild their society. They provide aid, leadership, and training. Outside of major battlefields the military is conducting research or maintaining security equipment. Some people in the military are lucky enough to never have to fire a shot at an enemy combatant, pirate, smuggler, etc.
This Facebook group fails to understand that, and as Synre said it is unlikely any of these folks would sign up for military duty. World peace is never going to happen until one human never wants to dominate another. Since that is probably never going to happen, the best you can hope for is peace through strength. You must make the cost of dominating another so high as to dissuade all but the most ambitious, driven people. You can't stop those people with just threats, they require action. That's where the military comes in. People can grouse and complain about it and work themselves up into a frenzy over the specifics, but soldiers allow the rest of us the option to live comfortably and do that.