The problem is that nationalists feel that the best defense is a good offense.
That sentiment is rife here in the US. Many of the more "conservative" bent actually take pride in the excessive military expenditures and actions our country engages in. It makes them feel safer, somehow, knowing that if WW3 erupted, we could turn half the planet into glowing ash.
I share your sentiment about self-defense forces vs standing armies.
One of the big reasons that this thinking exists, I believe, is because to a certain extent it is very true.
Look at the US in WW2. We got hit on our own soil exactly once, Pearl Harbor. Now look at all of the other parts of the world where that war was fought. Europe, North Africa, East Asia...all of those areas suffered greatly because of the war regardless of whose side they were on or who ultimately won.
Yes, the US lost a lot of people to the fighting and expended a lot of resources, but our core was never attacked and never in any real danger precisely because the US military went out and fought everywhere else.
That truth, and the strong position it left the US in after WW2, has influenced US policy making ever since. That is, to an extent,
why the US is running around the world playing Cop. Because if we can curtail actions and contain them in areas outside of the US then the
actual costs of those wars remain much less than the
potential costs of things snowballing and the US itself being threatened.
WW2 was a long time ago and it looks like attitudes are slowly starting to shift away from that mindset, but it's a powerful message for anyone who looks at history. Who came out ahead in WW2? The country that went out and joined in long before the war proper reached it. (Pearl Harbor was a strike, not an invasion, and mainland US was far from being in danger of invasion at that point).
Lessons like that take root in institutions and policy and take a very long time to change.