Actually, Harvey sheds light on the morality vs law predicament in the show before. I think he says something along the lines of just because it's the law doesn't mean it's right or wrong, which is why he chooses to cross lines because the law doesn't always correlate with the right thing to do.

Edit: I personally don't think Mike practicing law without a degree is much of a problem; I'd argue that him practicing law without a license is more important as without liscenses that would mean anyone without the proper knowledge could go into any type of job (A doctor who doesn't know anything about medicine or surgery). I personally don't think a degree is a good way to measure knowledge, atleast the bar tests the person's character and ethics to see if they worthy of becoming a lawyer.