Do you mean American mumbling accent or International English accent?
If the later, I fully agree and this apply the most to US citizens.
Last week I was having beer with two friend (one US one Canada) and a guy from LA came by, and it was completely impossible to me to understand one single word in his sentences (except for "fuck" and variants, which convey no meaning). He didn't seem to imagine that other people are different.
By the way, I'm French, living in China since 10 years, my English is rost because I use much more Chinese, but I usually can understand and make myself understood in International English.
For me the "hitishu" would have been obvious.
There is one thing behind this chitchat: English do not belong to UK or US anymore. It belong to the world. (Reasonably clear) Indian English has as many rights to life as have German English or Texan English or Aussie (which could well be the hardest).
I mean anyone who can pronounce words in English without causing you to interrupt them often, and ask to repeat themselves, regardless of their accent.
Another sad thing about this is the lack of "negative" feedback these people get, about their inability to communicate.
Most often native speakers are just too "kind", no one will ever say "I did not understand the half of what you just said, please speak slowly and pronounce words correctly". That is why most people never realize the severity of this issue.
You are correct about English belonging to the whole world, but trying to follow a common standard (British / American English) during education wouldn't be a bad thing.
Listen, people pronounce as correctly as they know how to. Do you know why people have an accent? It's because they can barely here the difference between sounds that sound alike, so they pronounce them the same. Many speaks of English around the world. Can't hear the th sound, they hear t or d. so they say tink instead of THing or Dis instead of THis. If you ask them to pronounce clearly, they will repeat the same thing over and over until they actually are taught to differenciate the sound. Until they can learn to hear it, isolate it, learn to reposition their tongue, mouth movement, etc. They won't be able to pronounce it "correctly"
Besides if they can do all that, that's still not enough, stressing the wrong part of a word, note, word not even sentence, can be a reason for you not to understand them. If they knew how to pronounce every single world the american way and stress it. If they don't link it or use the american intonation, you could still have a terrible hard time understanding them, unless they speak in an absolute monotone voice where it sounds like they are reading from a word list. That in itself is not easy as well.
It's not easy to acquire any accent, until you try it as an adult. You won't understand.
If it is like so, we should go back to slavery, it made no sense to abolish it.
> Indian English has as many rights to life as have German English or Texan English or Aussie
You are missing the point. It's not about "rights to life". No language (or dialect, or idiolect, or accent) has a "right to exist", or they all do. Who cares? (Also, German English? wtf?)
What matters are things like: Are you getting the results you want? Are you delivering good value to others (so that they want to give you good value back!)?
If your job doesn't require communication, speak whatever you like. If you're so damn good at your job that everyone else has to obey your whims, AND you don't care about the total effectiveness of your team, then speak whatever you like. But most people need to communicate, and for some people, poor accent becomes a dominant factor in their job performance. The responsibility is shared, but it falls most-heavily on the person who is most-different, because it's easier for one person to change than for a whole office to change. This, I hope and trust, is what znt meant when he said "professional responsibility".
Sometimes it cuts the other way, though. I'll give you an example from my own life. I am personally bad at understanding thick south-asian accents. I used to think all people from my background (Canadian anglophone) had the same problem. But I'm learning that I have more trouble than most people. That means it's mostly my problem. But if everyone agrees that so-and-so is very hard to understand, then it would be mostly so-and-so's problem.
This isn't about "rights" or "entitlement". It's about being effective. It's not the "law of the jungle", it's the law of gravity. And it's laughable, stupid, and somewhat offensive, to say that we might as well go back to slavery.
(Of course, sometimes I hear someone say "you have no right to speak your own language in my country". Those people are stupid and wrong. Fortunately, most people who say things like that are also not very good at other things in life, and they usually get punished by the marketplace, and we can ignore them. The rare people who are both powerful, and also stupid xenophobes, everyone else should cooperate to punish such people.)