Who is to say that, in the minds of some, serious negative moral judgement is NOT rendered against those who use poor grammar? I would posit that, particularly for the spoken word (we hear more people speak than we read their writing), many lose out on opportunities they might have enjoyed had poor grammar not caused a synaptic snag in the brain of another!
I imagine it has cost jobs, potential relationships and a host of other complexities in the lives of those who have not had the benefit of a fundamental education in the grammar of their native tongue.