You see, one could argue that the OP probably meant to say the mere existence of an institution whose purpose is to hone the skill of killing/destruction to maximum efficiency is a horrifying thing (hard to disagree), and it doesn't necessarily interfere with a people's right to defend themselves against an agressor in reality.
But the thing is, it absolutely does. People from the countries that haven't known war for decades or have always been the aggressor are equating any military with evil. Even if they say they discern between the perpetrator and the victim fighting back, there's still this underlying feeling of contempt and mistrust. And it is very much interfering with Ukraine's ability to defend itself.
At the beginning of the full-scale invasion, plenty of the so-called 'progressive' westerners were opposing arming Ukraine because 'weapon bad', berating queer Ukrainians posting about taking up arms to fight russia, asking others to disregard charities related to the military needs. People were willing to donate to foodbanks etc, but not to charities collecting money for the frontline needs. Which is fine as a personal preference, and we are grateful for any help, but when it turns into a stance where supporting the military is considered bad, it's equals holding a person's hands back while they're being attacked with a knife so that they can't defend themselves, and then nobly tending to their wounds.
And what's worse, it leads to complete disregard of the victims in the military. While the civilian deaths can draw at least some attention, the deaths in the army are met with indifference. And no, not in all instances it's by design of the military as a system made to kill, so the argument 'if it wasn't for the military, they'd be alive' doesn't work in Ukraine's case. In Ukraine's case, if it wasn't for the military, they'd be just as dead, and many more people would be dead as well.
And still, I remember a post of a female Ukrainian war medic interacting with the foreigners, and realizing that her fellow figters and veterans do not even make it to the list of those deserving sympathy in their eyes despite defending the others (with the adult Ukrainian civilians being far at the bottom of the list way below animals and 'great russian culture', but that's a different conversation). And the military are one of the most vulnerable groups in the Ukrainian society at the moment due to constant danger, exhausting 24/7 work and life-changing injuries. The only way they could become even more vulnerable would be if none of us were given weapons and trained in defense at all, an entire society becoming a target with zero chance of fighting back. So, you know, if there was no military.
So yeah, maybe sometimes it's a good thing to get your head out of your own ass and understand that the countries likely to become a victim of aggression have to train their military, because surprisingly, being able to defend yourself from being genocided is a good thing, and not, in fact, evil.