Concerned about younger brothers’ media consumption

So, I have a complicated relationship with my father. He’s pretty conservative, doesnt believe in autism, i think he was anti-vax for a bit idk if he switched on that, definitely has negative views on the LGBTQ community which sucks because I’m gay myself. Anyway, i think you can figure what kind of man he is just from that blurb, not great, and he was an even worse father to me and my siblings. He remarried about a decade ago and he had two boys, theyre great i love my little brothers to death, although i’ve been getting increasingly concerned about what theyve been watching on youtube and tv in general. All they care about is war and police and killing, theyre 8 years old. One of them is a little less concerning as he has other interests outside of that but the other is just a world war 2 encyclopedia (he even knows like a list of warcrimes off the top of his head like wtf dude) and i think was watching like police bodycam footage he found on youtube at one point, just crazy. What im asking for advice on is, my dad and his wife are clearly unequipped to raise children in the modern age or just simply don’t care theyre so hands off and are surprised that im even able to manage the boys and communicate things to them, like youre the parent dude how do you get through your day to day. ive tried giving them more positive things like books and even hacked some 3DS’s for them to maybe get them off their ipads and onto something more kid friendly but theyre fully hooked on war, it doesnt help that i think theyre both autistic (which my dad doesnt believe in) and i feel like this is a hyperfixation for them. How do i explain to them that war is not something for kids? Everyone in the family is uncomfortable with the enjoyment they get out of it but no one says anything! Its so frustrating and i dont want my little brothers to be those weird kids in school that just talk about war all the time and how the army is the greatest thing in the world, because it really isnt and i dont want them to fall into this propagandized grooming trap the USA has set up idc if thats me being an annoying leftist its just true. I just dont know how to address this without my dad getting angry somehow (which i feel like he will honestly if they tell him what i say). It just feels like this is my responsibility as their older brother, sorry if this comes off as rambling.

TLDR - how do you explain to an 8 year old that war is horrible and not for kids in a way that is appropriate