All the hatred aimed at Ares is ...well.. according to plot. But he is a prime example of a Tragic/Failed Hero, and not necessarily a villain of any kind.
It's the bug in the Divine Skill system the MC has pointed out several times, and which we've seen examples of ranging from Little Things up to Ruti, who can only just resist her Skill-driven urges as [Hero] with demon-derived drugs. And even then she admits that a real call on her Skill would make it impossible for her to ignore the Urge..
Ares not just lives his Skill, he has become it to the point that it drives and consumes his entire existence.
Being denied the possibility to Aid the [Hero] not once, but twice, and this time terminal, his Skill, along with any semblance of reason goes haywire and tries to find a way to "correct" the world so that the programmed system works.
For him. And just for him.
Which is exactly the thing the MC warned for what could happen if a strong Skill gets denied. And [Sage] is not just strong.. It's one of the top-tier Skills..
It's a major flaw in the system, and the demons are happily abusing this feature...