Vulcans and Spock

I've thought about this in the past.
Vulcans generally treat Spock, who is half-Vulcan and half-Human (for which I just turn off my understanding of evolutionary and developmental biology), as having a disadvantage toward being as disciplined and logical as other Vulcans. Supposedly, this is because the Human component makes him more emotional and less rational.
This makes no sense.
I don't say that because I think that Humans are extremely rational or anything like that. The thing is that, as I understand it, Vulcan logic is cultural. Specifically, Vulcans developed their logical culture as a reaction against their extremely chaotic and destructive nature. Becoming logical allowed Vulcans to rise up from their very real savagery and become a very well-developed intelligent species.
So, innately, Vulcans are a bunch of savage brutes, more so than Humans, and their culture, reacting against that, has allowed them to become extremely rational, more so than Humans. The thing is that culture is not built into one's biology. A half-Human half-Vulcan, raised as a Vulcan, should be just as logical as any Vulcan. Indeed, a Human raised as a Vulcan would actually have an advantage, since his urges would not be nearly as strong as those of his Vulcan counterparts.
Well, that's it. For any of you who know Star Trek: What do you think? Am I wrong? Did I miss something? Or am I right, and there's a big hole in the Vulcan treatment of Spock?