Well Trish did take on the responsibility of keeping the people safe. And in the only time that Dante could even partly be blamed for (After the real Hell Gate had been opened) the Order's Angelos and the Savior moved in right away to exterminate the Demons. In a way them getting Sparda actually saved lives.My problem is not the Order or how powerful they are. It's the innocent people behind killed in the middle and they were totally giving a damn.Very unDantish! But them again they gave Sparda to the Order just to have fun, which is the same of giving Daesh some powerful nuclear bomb and giggling how fun it will be.
Sure, but in terms of what we were talking about he's not that old. I doubt he's near as old as Dante, for example.But he is not that young either and he is a wacko scientist.That's why he is a freak.
I don't really agree with your assessment of how they did his character, though I also would have rather they finished up the third volume of the manga.That's why I lament so much the lack of the third part of the DMC3 manga and how poor and superficial they went with Vergil's character.Some files go on how evil he was while other media gives emphasis on how he isn't hostile to humans, because a child of Sparda can't be hostile to humans.The only time Vergil shows some kind of repulse about what Arkham have done , it is when he mentions Arkham's wife was nothing more than a loving person.Even when Arkham goes out to kill his daughter" because that is what Vergil wants", Vergil didn't say yes, but he didn't say no either.So my conclusion is that he is whatever for humans and demons, UNLESS they touch his precious Sparda's power.
In terms of Humans and Demons, I think he hated the latter but was more or less ambivalent about the former. If any Humans got in his way he wouldn't have much of a problem with killing them, and casualties brought about by things like raising the tower were an "ends justify the means" thing, but he didn't really have animosity towards them either, after all his father saved Humanity once. Overall he just thought they were weak, and that the human part of him made him weak.
While Humans using Demons to get more power is something he could probably understand, I really doubt he'd tolerate anyone using Sparda's name - Much less his actual legacy or blood - To do it.