Actually, I'm not aware of a single example of honour killings in Iran. If you want a better example of a "pinnacle of Islamic rule" Saudi Arabia (the US puppet/ally) would be much more appropriate. Other candidates would be Indonesia, for complicated reasons. Since Indonesia is primarily ethnically non-Arabic, yet Arabs are given higher social status and considered more "true" to Islam (due to "Arab supremacist" themes embedded in the Koran, not the least a prohibition (often ignored) against translating it), much like Spanish-descended people in Latin America (who have not "bred" with natives and are technically a non-Latino minority). You could probably make a decent argument for why Indonesia's Muslim population is so fervent -- compensation for feelings of inferiority due to not being Arabic is the likeliest.
It's also important to realize the context of why they believe what they do. Essentially, it's a form of semi-primitive tribalism focused on the family unit. Most societies, as they progress, inevitably abandon this model or heavily reduce its importance, but it is a very major underpinning to the Abrahamic religions. Essentially, it is patriarchal and focused on the absolute divine right of the patriarch to do whatever he wants. The fact that the prohibitions in the Old Testament limiting the power of a patriarch are so weak attests to the fact of how much control a man might have over his family. This sort of tribalism, applied on a larger scale, is the root for racism and nationalism, as well as other evils. Its primary focus is simple: defining a group so the members know whom they should include or exclude. Culture is another form of in-group/out-group xenophobia, which is why liberals tend to embrace multiculturalism, while conservatives tend to be far less adventurous.
As far as Sharia goes, it has parallels in Judaism and Christianity (and, indeed, parallel groups attempting to practice similar systems) because it is based on the concept of the supposed authority of the patriarch. This is something which supports not just calcified familial systems, including caste systems, but also feudal monarchies (the concept of divine right having been directly invoked by European kings). In this case, honour and prestige become huge factors -- anyone who has read about the Victorian high society would realize that, while there wasn't a whole lot that was illegal for upper-class people, but that they relied so much on being seen as "gentlemanly" and on being approved of by their peers that they were forced to hide any behaviour not condoned by their society. It's similar to the Inner Party of Nineteen Eighty-Four, with the proles being far more free (albeit while undergoing deprivation) than Party members.
In the cases of feudal societies or societies transitioning out of feudalism, rising egalitarianism could compel the remnants of the feudal nobility/aristocracy or of the general elite class to struggle to maintain their illusion of control and authority -- for instance, through censorship, as in the case of Thailand. In other cases, religion can be used as a proxy in an attempt to bolster authority (which, in the Middle East, has been well-documented with Saddam Hussein's increasing fundamentalism and religious authoritarianism as his rule went on, likely as a cynical attempt to keep Iraqis under his thumb). Many dictators tend to be adaptive opportunists who will adopt a tool (like religion) if they need it to get into (or stay in) power. Another good example is Hitler's embrace of Catholicism (and acknowledgement of Lutheranism) during his rise to power, in an attempt to gain more followers and to turn a largely ethnic conflict into a religious conflict as well, with the simultaneous replacement of pre-existing religion in his inner circle with a home-grown cult, complete with mystic origins. The rub for Hitler was that too much alignment with Catholicism would put him into the classic conflict that had dominated Germany for centuries -- the authority of the Pope versus the authority of the Holy Roman Emperor (or dictator). For small-time dictators in the Middle East, many of whom are Sunni (rather than Shi'ite countries), their religion is somewhat decentralized, much like independent Protestant groups in places like the United States. This gives them the easy ability to simply use religion as a political tool (to be fair, some religions seem almost tailor-made for it).