Random observation, it occurs to me that Gunn is kind of the modern Hotlz - both became vampire/demon hunters and leaders of the respective teams in their time. The main difference of course with Gunn coming to work for Angel.
I wonder, if circumstances had been different and Holtz had first met Angel when Angel had a soul (and of course, if Angel hadn't personally been responsible for the death of his family) would Holtz, righteous man that he is, still try to kill Angel; or could he have become an ally like Gunn did? And conversely, how might things have gone down between Gunn and Angel if they first met while Angel lacked a soul...?
“In the game of chess, you can never let your adversary see your pieces.”
I don't think so I think Holtz is more a product of the time, the sort of black and white outlook of things, soul or no soul he's a demon and is there by evil, and Holtz is therefor justified in any of his actions no matter how evil and wrong they maybe, part of Holtz's issue is racism in a way.
Gunn has more a modern outlook to things, he knows Angel could go evil pretty easy, to the point it's not just a case of Angel going bad like a normal person would, but literally a snap of the fingers, a moment of weakness or a spell could bring Angelus out without warning, yet Gunn doesn't look at that, he see's Angel for who he is not what he is so imo even if Gunn men Angelus first he would judge Angel for being Angel.