I see him skipping straight to shouting at his sister when he finds out how serious her condition is, being negative even when she requests him not to be and failing to even acknowledge her opinions about the bright side of life, and then being absolutely and unremittingly scathing towards a mother who cannot help her condition (even addressing it in similarly dismissive terms to Riley and Leah, which is a whole extra realm of douchebaggery). He also mugs old men instead of even asking them for help, and he wouldn't have been fighting that elf to the death if he'd had the sense to run away with Jon and Meji, but he was already crazy enough to keep blasting away even back then. So yes, I think Ian was on the road to crazy town long before he got high on godjuice.
Maybe I see him as such a douche primarily because of how he speaks of his mother. I have a condition like hers. I walk a fine line between "can't help it" and "won't help it." Sometimes it's one, sometimes the other, sometimes it's even both. You know what doesn't help you to fight a condition like that? Judgement, dismissal, and scorn from your loved ones. In fact, the wrong dynamic can aggravate the condition a LOT, especially when you aren't medicated for it. I just barely lived through a time when I wasn't diagnosed or medicated, and my family had no clue how to respond to me or my behavior, and that left some pretty deep scars (both psychic and physical, and not only on myself). Is his mom right to behave the way she does? No, probably not, and I know it isn't easy to live with, but that doesn't make Ian any less of a dick for how he responds to it.
Though, honestly, I've distrusted and disliked Ian from this moment on:
http://www.errantstory.com/2003-09-24/150 He's never even met an elf, but he has no hesitation at all about labeling them all as monsters and spreading that view to others. Once again, he has the opportunity to behave with grace towards his fellow living beings, to give them the benefit of the doubt, and it doesn't even occur to him. He chooses hate without ever stopping to consider the alternative.
I find that very hard to admire or excuse, and I certainly can't blame it on power he didn't have yet.
-_-'