You're right: Heinz isn't a bad person. In fact, he's downright decent. If any of us met a guy like him on the street (and weren't introverts or otherwise easily turned off by people) we'd warm up to him pretty quickly.
The problem is that this isn't our story, or even his; it's Van's. Van, who has a legitimate and justified reason to want revenge. Van, who could probably make up with Heinz if the latter truly apologized and tried to work together with the former on making things better for Van's subordinates/family and Vida's races.
But that unfortunately can't happen for one big reason: the only people around Heinz for him to listen to are people who listen to the people who listen to the people who listen to the people solely responsible for this situation (Alda, Bellwood & Rodcorte). It would take a pretty big event to upheave Heinz's entire faith and Van's Mental Corruption and get them into the same place and of a mind to talk things out without ignoring the other's views, and the way the story's written there's nothing that can facilitate that before Heinz drinks the Kool-Aid and becomes a legitimate antagonist to Van. I dunno, Fitun certainly didn't. Maybe Asakura could.
In a 'Normal' World he do will be decent person, but this world all but normal. Its dying world, divided, full of corruption (internal and external). There need for visionary and revolutionary, not for cookie-cuter hero.
Another problem that he working similar like a spokesperson for a corrupt government, can say only written BS that higher-ups wrote for public (and believe in it) but public see BS and questioned back.
Only thing i disagree, probably because i read novel, that Van
Can forgive Heinz. I think that the moment with Priest and Spear show up how insane and angry Van is. He too irrational to simply forgive him. And Van himself became aware of it.
As for 'event' it need to be on the same scale as Darcia's torture. Due to it instigated by vampires its second biggest F* you that evil gods given to Alda (first sealing Bellwood, by a different god), breaking his most treasured puppet (carefully prepared vessel for Bellwood) by opening his eyes to reality. Sadly not enough.
If he could witness which measures Alda undertook in final battle.
Asakura???
I definitely think its the author's intent to show that Heins isn't a bad person. The tragedy of it all is that despite that, conflict between him and Van is inevitable.
While I can understand why some of the people here are 100% on Van's side, I think closing themselves off to even the idea of Heinz being a good person, making up stuff to convince themselves that everything he does is somehow evil, just prevents them from fully enjoying this story.
The intention is there. The fact that there is such discussions about Heinz (and divided to such extent) shows that author followed in right direction. Unfortunately there something missing there. Some kind 'secret ingredient' that prevent him to join the rest of proper characters. Like he under cooked. I blame author inability/lack of skill to properly convey what is Heinz is. In fact other enemies, despite being simple, is understandable and working great.
Probably similar problem with modern western villains, trying make them 'relatable'.