"The possibilities in Arabic for the use of figurative language are endless; its allusiveness, tropes and figures of speech place it far beyond the reach of any other language... Arabic loses on translation but all other languages gain on being translated into Arabic."
-- Joel Carmichael, The Shaping of the Arabs (1967)
Arabic is a tremendously complex language, which means that the Qur'an is a subtle text. Those who translate the text into English and those who interpret the text literally are in essence committing the same sin of truncation - they are taking something three-dimensional and reducing it to two. That missing dimension is the cultural and symbolic context which the writer in Arabic embeds his words - a rich layer of meaning that is inferred rather than simply transcribed.
The specific way in which this occurs is difficult to explain. Blogger H.D. Miller described it thus:
individual Arabic words are formed from simple three letter roots. To these simple roots suffixes, prefixes, and infixes are added, and vowels are changed to produce a large number of individual words which have, either actually or metaphorically, meanings somehow related to the idea behind the simple root. For example, the Arabic root k-t-b is expressed as a verbal infinitive as kataba, meaning "to write". From that basic root we can then get the words kitab "book", kAtib "writer", maktUb "written" (with a metaphorical meaning of "predestined"), maktab "office", maktaba "library", makAtaba "correspondence", kutubi "bookseller", kuttAb "elementary school", istiktAb "dictation", makAtib "correspondent" or "reporter", muktatib "subscriber", and about a hundred more variations all produced from that original three letter root.
All of the words springing from the triliteral root k-t-b have that similar three letter sound to bind them together, which means that each of the words shaped from the root, when spoken, are capable of evoking any of the other words shaped from that same root. To this, an extra layer of complexity and evocativeness is added by the fact that many of the Arabic consonants sound remarkably similar, so that there are two h's, one "hard" and one "soft", two s's, two t's and so on. This means that when you say k-t-b you're also evoking q-t-b "hunch" as in "hunchback", q-T-b (with the "hard" T ) which gives the root meaning of "to gather or collect", and about a dozen other groups of words. To the native speaker all of these various meanings resonate at either the conscious or unconscious level. This is what I mean when I speak of evocative and allusive, this feature of Arabic which links together hundreds of words, many of them with very different meanings.
This is why any theological interpretation of the Qur'an that starts from an English translation as its source text is immediately invalid. English translations exist, of course, and are not in themselves harmful. In fact they are valuable in providing the baseline meaning from which one can proceed with tafsir (interpretation). However if you begin and end your scholarship of the Qur'an with the translation alone, then you are not talking about Islam. You are talking about a reflection of Islam as seen from the translator's eyes, filtered through your own biases.
For example, three well-known translations are by M.H. Shakir, Abdullah Yusufali, and Marmaduke Pickthall. Consider the differences in their translations for Qur'an 3:23:
YUSUFALI: Hast thou not turned Thy vision to those who have been given a portion of the Book? They are invited to the Book of Allah, to settle their dispute, but a party of them Turn back and decline (The arbitration).
PICKTHAL: Hast thou not seen how those who have received a portion of the Scripture invoke the Scripture of Allah (in their disputes) that it may judge between them; then a faction of them turn away, being opposed (to it)?
SHAKIR: Have you not considered those (Jews) who are given a portion of the Book? They are invited to the Book of Allah that it might decide between them, then a part of them turn back and they withdraw.
Immediately we see that Yusufali interprets this as a faction that has declined arbitration via the Qur'an, whereas Pickthal sees the rejection as outright opposition to the Qur'an. Meanwhile Shakir interprets the passage as applying specifically to Jews, even though in the actual Arabic there is no specific mention of Jews aka "Yahudi" or the tribe of Banu Israel therein. Each of these writers carries baggage with them and that shapes how they interpret the passage. By cementing the passage into english, the meaning is rendered static. All the allusiveness that Miller described is irrecovably lost.
This is not to say that muslims don't adopt such strict interpretations as valid. The problem here is that most muslims simply don't have time or knowledge to go through the Qur'an line by line and translate the text. This creates an opening for those with agenda to define the faith and wrap their own biases in Qur'anic legitimacy.
While I certainly believe that there is a "correct" interpretation of the Qur'an, the fact remains that Islam is a living religion. But he who interprets the Qur'an in the worst possible light is no more representative of Islam than he who interprets it in the best. Since we have empirical evidence that one billion muslims worldwide have not risen up in slaughter against their non-muslim neighbors, and that the actual number of muslims who interpret the Qur'an to justify violence is a tiny percentage of the total number of believers, there's nothing innate about Islam or the verses of the Qur'an that leads to such behaviors. Anyone who asserts, for example, that verse X:YY of the Qur'an permits muslims to lie to unbelievers (taqqiya), for example, is making a factually untrue statement. The correct statement would be that such a verse has been used to justify lying to non-believers, but until such time as someone proves that a significant fraction of muslims habitually lie in such fashion, it's merely an anecdote, not an observation with any kind of predictive power.
The average muslim does not walk under a cloud of Qur'an ayats burned into his brain, dictating their every move. Muslims interact with others based on the same types of prejudices, experiences, good and bad knowledge that everyone else carries. The Qur'an is a generalized influence, but not the sole one and ccertainly not a specific one. While I certainly wish I could carry the entirety of the Qur'an in my brain and have relevant ayats appear in memory as life proceeds apace, it's simply not possible. Rather, I recite the Qur'an in Arabic as a duty and base my relationships with my community on the sermons and teachings of my authorities and role models. And sometimes quote it on blogs in responses to someone (usually non-muslim) telling me what Islam really is.