This is such an interesting thing to discuss. Of course I agree with you, guns, war planes, missiles are obscene, every dollar spent on weapons when people are dying from dirty water is revolting, our armies seem to be deployed primarily to expand and protect empire. But while as a twenty year old I was firmly anti-military, got arrested at anti war protests, personally I began to look at the military differently after the Australian army's deployment to East Timor, in Bougainvile after the ceasefire, and the federal police deployment to the Solomons after the civil war - I believe these deployments protected civilians from real danger. Perhaps as I have come to understand my own limitations, I am less bold in my imagination as to how long it will take us as a species to transcend selfishness and violence. For the foreseeable future violence and war will be part of the human experience, this doesn't justify its glorification, it doesn't justify empire or drone strikes on weddings, but this realisation has utterly dismantled my previously held belief that abstaining from all preparation and participation in violence and war is the responsible, progressive position I thought it was. The abysmal quality of political debate doesn't require us to reduce the sophistication of our own thinking to simplistic characterisations, we're capable of understanding that state sanctioned violence at the police or military level is supported by both good and bad faith agendas, and perhaps only at the extremes it is possible to tell which is which.
I don't think it's a black and white thing. It's entirely possible to support Australia's peacekeeping deployments to Timor Leste and their humanitarian deployments after natural disasters while being opposed to their deployment to them murdering unarmed Afghan civilians.
I can't comment on other militaries, but the ADF does a lot of good, alongside the bad. They do a lot of critical work in the Asia-Pacific region, both peacekeeping and disaster recovery. At the end of the day, they're subject to the whims of whoever happens to be running the country at the time.
To quote the gun-loving Right, sometimes the only person can stop a bad guy with a gun is a good guy with a gun. The better solution is to prevent there from being bad guys with guns, but this isn't always possible.