Conflict is a necessity in a world with limited resources. A species evolving in such world will be adapted to that reality. Even in a robust economy people compete: jobs, resources, relationships, housing yadda yadda
You can't extricate conflict from a species that has a survival and reproductive imperative.
Again, war is only one way to resolve a conflict. Indeed, it does not actually resolve the conflict, that happens at the negotiation table. All the killing is so that one side will have an advantage at said table. Let's not glorify that particular negotiating strategy - slaugtering innocent bystanders, that is - beyond its honestly earned merit.
War is actually a subclass of a more general case--the use of force.
At it's most basic level you can't take it off the table, it's part of most negotiations--although often in the form of calling the cops if the negotiating tactics break the law. The fact that the cops would be called in many cases pushes the actual use of force almost completely out of the picture, but it's still the threat of force that causes this. (For example, slavery. An employer can't just grab someone and chain them to a machine and expect to get away with it. Only the potential use of force stops the scumbags from doing this.)
There are a number of highly dubious assumptions here. Force is generally not on the table, unless you are dealing with psychopaths. Of course, psycopathy is not rare, so some negotiations can be expected to involve them. But most don't.
Your mischaracterizing of psychopaths as 'scumbags' doesn't help either - it's based in your commonly expressed but false belief that there are 'good guys' and 'bad guys', and that this dichotomy is a useful one. It's not.
Ultimately you are making the same argument that the religious nutters do, when they say 'without God, what's to stop people from raping and murdering whenever they feel like it?'.
You simply replace 'God' with 'violence or the threat of violence'. But the vast majority of people need neither Gods nor violence in order to behave in a civilized and moral fashion. Indeed, apart from the mentally ill, everyone acts according to his morality in a way that they consider 'good'.
Without the threat of violence (or hell), I rape and kill as much as I want - and the amount I want is 'none at all'.
There are not 'good guys' and 'bad guys', there are just people who share your moral framework, and people who have a different moral framework. Within their own framework, everyone (apart from the mentally ill) is one of the 'good guys'.
And in a civilized society, very few people need the threat of violence to prevent them from gross violations of the golden rule. What you perceive as 'bad guys' are people who either set their priorities differently from you - and as a result choose to punish moral transgressions that you do not recognize as immoral; Or who are misinformed, and as a result choose to punish behaviours that they falsely believe to breach their personal moral code.
Most violence and crime is perceived by the perpetrator as either punitive, or self defence.
Even slavers resolve the moral question of whether it's OK to "just grab someone and chain them to a machine" by first establishing the firm belief that the slaves are not 'someone'. Animals are not entitled to the same protection as humans, so by declaring your victims to be non-human or sub-human, you can justify enslaving them. Nobody enslaves someone simply because nobody threatened to use violence to stop them.
