The name Allāh has chosen for His religion is الإسلام - Islām.  He, subhānahu wa ta`ālā, has also provided a corresponding name for any follower of that religion, and it is مسلم - Muslim. 

 

"He [i.e., Allāh] named you "Muslims" before [in former scriptures] and in this [revelation] that the Messenger may be a witness over you and you may be witnesses over the people…" (Soorah Al-Hajj 22:78)

 

Sadly, due to the pronunciation rules within the English language the word Muslim gets pronounced as "muzlim" and Islām gets pronounced as “izlam”.  These are incorrect pronunciations and not translations.

 

We can excuse English-speaking non-Muslims for these mispronunciations, but as Muslims we ourselves should pronounce correctly these nouns that identify us.  Here are some of the reasons why:

• It is part of truthfulness to call things by their correct name. 
• One of the signs of knowledge and intelligence is to know things by their correct name. 
• Consider for example, when we see foreigners (to English) mispronounce words and it just doesn't sound right or eloquent; but we excuse them and do not follow them in their mistakes.

You may say "it's not a big deal!" or (a common saying) "the Muslims have bigger issues to deal with!"  In response to that, we ask you to please reflect on some of the following points:

1. The Prophet (sallAllāhu 'alayhi wasallam) said, ‎"Do not consider anything insignificant out of good things..." (Saheeh Muslim, no. 1209).
2. Certain issues are easily under your control, so you should take action.  Allāh will reward you for even small deeds done with sincere intent.
3. If you strive to become someone who guards the small matters, the bigger issues are less likely to escape you, inshā Allāh.

There have been suggestions that the English pronunciation changes the meaning of the word into something offensive, is that true? 

If the English pronunciation ("muzlim") were to be transliterated into Arabic, it would spell مزلم.  No entries for this exact word^[1] were found in the Arabic dictionary, Al-Mawrid (and also not in some of the other less well-known dictionaries).  There may be other derivatives from this word, however, the only apparent negative implication of this particular word (مزلم), as a result of mispronunciation, seems to be the corruption of the pure sound, wAllāhu a`lam.  The closest word to this pronunciation is مُظْلِم and even that is not an offensive word, as shown below:

مُظْلِم (adj.) = black, dark

Therefore, there does not seem to be a pressing need to start a campaign to educate non-Muslims to the correct pronunciation, rather we should start with ourselves.  Hopefully, non-Muslims acquaintances will pick up the correct pronunciation when they listen to us speak.

Although, this brief article deals mainly with the word 'Muslim', the same principle applies to all other (untranslated) proper nouns from the words of al-Islām.