Your question is very broad and I'm having difficulty formulating a concise answer to this, so excuse me if I seem to ramble a bit. I hope the answer is interesting and insightful anyway.

On idealism

To be honest, I think you're being too idealistic. Yes the ideal is to be neutral and fair, but that's not always never possible is it?

Let's go back to May 1982, the southern Atlantic, off the coast of Argentina. What happened there, was it the British invasion of the Islas Malvinas or the liberation of the Falkland Islands? Pick one description and you've picked a side. You know what? Nevermind the 'invasion'/'liberation' part. Pick a name and you've picked a side! Call it the 'Falkland Islands' and you have justified the British actions; call it the 'Islas Malvinas' and you've justified the Argentine actions.

Of course petty semantics like this don't stop us from doing proper fair and balanced history. Once past the naming issue, military historians can describe the British amphibious operation and the Argentine defensive response without passing judgement. (Or is 'defensive' a non-neutral word? Does it imply more than I want it to? I'm starting to doubt myself...) [anecdote warning] I have had the pleasure of studying military history with cadets of a military academy and it was great to see the way they studied military operations without judging who was fighting but only judging how the fighting was done and why it was done that way. It was very functional and methodical (they sure love METT-TC). [end anecdote]

You're also being too idealistic by claiming that no war is justifiable. If starting a war isn't justifiable, is continuing a war? Once the Argentines moved to liberate the Islas Malvinas and the token British defense was defeated, was not the war effectively over? Were the British justified in sending a task force to the Falklands to reopen the hostilities? I'd say that by claiming that "no war is justifiable" you have not only opened a can of worms but also passed judgement on every nation which was ever involved in a war. This is not "neutral and fair", this is moralistic and self-righteous - precisely that which a historian should never be.

On atrocities

Historians don't revere or justify persons and their actions. Historians look at the circumstances of persons and events to contextualize and (try to) understand them. Burning a city to the ground, killing and enslaving its inhabitants, can be called an atrocity. When this was done, it was often sound strategy since it made other cities join or stay on the offender's side. No city wants to suffer the same fate. Something being a sound strategy doesn't necesarily justify it, but it does provide context for the event.

The bombing of Hiroshima and Nagasaki can be called an atrocity, but it was just a continuation of the existing bombing strategy by other means; that bombing strategy at the time being justified by an air power doctrine which at least in theory made sense. When Giulio Douhet conceived of air power during the First World War, he set in motion twenty years of military thinking which culminated in the bombing of Guernica and the strategic bombing (or is it 'carpet bombing', or 'terror bombing', or 'offensive bombing', or ...) of the Second World War. Bomber Harris was not (just) being vindictive when he embarked the RAF on the strategic bombing campaign; there was (at the time) pretty sound military theory behind the idea. Again, this does not necesarily justify the flattening of cities, but it does provide context.

Conclusion

This is basically how I think historians should treat military history. Not as idealistic as you; more functional and methodical. I won't comment on how it has shaped my personal views, though they can be partly constructed from what I've written above. Again, I hope this answer is useful to you.

Now this is going to sound screwed up but through my study of history, I've come to the belief that military action is often the fastest and most lasting solution as long as it's had it's proper planing.

I can't blame past empires and peoples for aggressive wars and atrocities because arguably wars and atrocities built empire and civilization.

From what I've seen there are historically two types of wars; resource and political. A third type could be called moral war but most examples of "moral" wars often have political or resource motives that out weigh the "moral" aspect. Often the moral aspect is polished or pushed after the war to give a good guy/bad guy lean to it.

Modern political correctness is throwing a hickup into the natural rhythm to resource/political wars and making them more costly. And often could make maters worse. Example: Imperial Germany was waging a political war like all other European powers in WWI but was called evil and in the wrong and punished harshly which bred anger in defeated Germany because they were blamed for a war they didn't start. That bred the anger and hate that led to WWII.

I'm rambling but in short, my study of history has affected my political out look that political correctness makes things worse

I think I did become, in a way, more moderate and a little bit conservative.

Basically the common intellectual idea today is that conflict is inside socities: between the oppressor and the oppressed, power elites and common folks.

The more history I learned the more I see it is not quite so - conflict is mostly between societies, not inside them, and on a very rough average, common people generally did not hate their power elites / kings / nobles / whoever but rather saw them as natural leaders to lead them into looting some other society and distribute a good amount of loot amongst the common folks. Frankly if you are a dirt poor Roman soldier you won't see yourself as oppressed and Caesar as your oppressor. Rather he will lead you into battle looting Gaul and if you survive you end up with quite some money, maybe slaves, and maybe land in a province.

We can say something similar to gender relations -women were not so much oppressed as much as attempting to be sheltered at home from the brutal fallout from all this fighting and looting that happened between societies. Once you see every man from a neighboring country as a potential rapist if he comes over campagining and looting, suddenly housewifing in a well defended home looks like a good idea. And as for all this fighting you need a lot of children in order to have a lot of soldiers, and dad is often away trying his durndest to loot the neighboring country, once you see boys as cannon fodder and girls as cannon fodder makers, once you see war as the origin of everything, all these gender roles stuff suddenly start to make some sense without assuming either social oppression or some kind of weird unchanging biological programming. I can say similar things about wealth inequality, aristocratic privileges and so on.

I am not saying I approve of all this or that it made me some kind staunch conservative, as it didn't, as the whole thing is obviously not ethical, but I am simply saying I got more distant from the usual Englightenment-progressive view of seeing socities rife with interal conflict between oppressive power elites and oppressed common folks, and I see them more like having a swell cooperation between the powerful and the powerless for the grand purpose of looting the neighboring country. I guess it made me a cynical moderate.