when you equate it with throwing a rock at a tank, it sounds like you believe we're describing everyone who engages in the concept of violence as evil. that's not it at all. you have to investigate the purpose of the violence, and in the case of a military force, the history and current goals of that force. in the US's case it's been pretty much universally evil since ww2, leaving millions dead always for the purpose increasing the US's relative strength in juxtaposition with non-aligned states.
just take the tally: korean war - evil, up to 2m dead. vietnam war - evil, up to 4m dead. iraq war - evil, up to 1m dead. all these are cases of the US just deciding it doesn't like the way the people of a particular nation/state half the world away is handling their affairs and that it would prefer to go in there and wage war to precipitate an outcome more to its selfish preference. it's bad all the time, throw in what was done in libya and syria, what's going on in palestine and yemen, what the US daydreams of doing to iran, when none of these places has shown aggression toward the US.
The people who join the US's fighting forces are signing up as enablers in violence on a massive scale, they are agents of a great evil, and they do so entirely willingly. a lot of them are small people that grew up playing violent video games and want to go off and witness bloodshed, others are scions of people who have long served empire for profit as part of family tradition. many are tricked by american fairytales and bedtime stories but they should know better before they sign the dotted line to risk their lives and end many others. We can hope the ones who are good, who are simply misled, will change their minds and stop abetting in this worldwide wholesale slaughter, but that will only happen if we speak clearly. Against fascism. Against empire. Against death to increase the profits of a very narrow segment of a population thousands of miles away from the sphere of battle.