Let's go back and analyze the first post, step by step.
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'D'yer stop at Salfod preeky?' one asked.

Here's a person who has made the simple error of prouncing the c in 'precinct' as if it had a hard c rather than a soft c.

Why might a person do that?

1. Never heard it pronounced and is sounding it out wrong.

2. Is deaf or partially so.

3. Is autistic or similar.

4. Learned the pronunciation from someone else with similar problems.

None of this qualifies a person as stupid.
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The driver (East European I think )looked blank for a minute so I translated

'She is asking if you go via Salford Precinct.'

This violates one of the basic rules of politeness in our culture. We don't speak of a person who is present in the third person. Not unless we are teasing or the person is a baby.

I'd give you odds of 9 to 1 that 'She is asking if you go via Salford Precinct' was spoken in an openly contemptuous tone.
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'Oh, sorry' he replied 'No - You are better with the 37. It will be along soon.'

Well, she gave us both a look that could kill.

'Fuckin wogs. Can't even talk proper...'

They both stormed off amidst fits of giggles from most people in earshot.
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I bet the giggles weren't giggles at all. They were sneers and sniggers. And I bet they preceded the exit. But I also bet they didn't come from most people. Just a few.   

And then the 'chavs' responded with the first rude things that came to mind.

I'm not surprised.