When you're teaching a foreign language, explaining why pronouncing a word correctly is important is often a rather abstract concept for students. Often, they think you're being overly fussy or pedantic. The truth is that this impression is not always a false one. I've heard teachers who are from other countries go out of their way to correct an accent because it represents the pronunciation of native speakers from another country. Particularly, a lot of British people want to "correct" North American accents when the student's speech patterns would be comprehended just fine anywhere in the world.
My feeling has always been that, as long as what you say can be understood, it doesn't matter if its the pronunciation a native speaker would use. However, sometimes it's very important to get it straight so that you are not a laughing stock. If one ever needed a more perfect example of this, one need only turn to the very well known (amongst expatriates) Japanese Self Defense Force Navy commercial:
The words on the screen are telling you what they mean to say, but what you hear if you're not reading along is "semen sip for love." Seeing a bunch of dancing, prancing sailors say "semen sip for love," does not conjure up the intended image of peace-loving protectors so much as gay sailors who enjoy nothing more than some round robin acts of fellatio.
So, if you ever need to prove how important it is to get the pronunciation of words correct, you can just show this video to the students and explain the meaning a native speaker is going to get.