Everyone’s just arguing about this from two different ends. I’ll pick two random posters who have vociferously argued their sides: Lior and PAA. (000646 is taking an entirely different tack on his side, so I won’t use him.)
Lior is saying that we can justify ourselves because we have the truth, and that’s what makes us different from them. Torah-true Jews would all agree.
PAA is saying that we can say that all we like, but the world at large, or even we in some uneasy corner of ourselves, can’t always justify it that way. After all, ISIS (seems to) think that they’re right and they’re divinely ordained, in which case to an objective outsider, we are basically identical, and, in a way, each side is hypocritical if it criticizes the other.
Neither of your views would seem to be contradictory. On Lior’s side, the only way they would contradict each other is if Lior then went out into the world and argued his case secure in his knowledge that he was right and they were wrong, he would end up against PAA’s roadblock that nobody would believe him and nobody would care. On PAA’s side, the only way they would contradict each other is if PAA took his argument to 000646’s conclusion which is that (or so it seems to me) that in this day and age, what we USED to do is no longer moral- a slippery slope that one could use to apply to many things that can end up being a bit dangerous.