So do you descend to their level, then?
And if you do, whats the difference between the two of you?
No, you treat people as they treat themselves. This is not the same as an eye for an eye. However if someone treats themselves bad, of course they'll treat you bad too.
As an example, Sam is an ethical human, she loves herself, and a casual observer can see this by how she treats herself. Someone like her should be treated with the respect that she gives to herself.
NOW, you have other people who don't respect themselves, who aren't ethical, who hate themselves, and to the casual observer, they will carry themselves in a very self destructive way. This sort of person you treat differently, you treat them as they treat themselves.
So thats the rule, you treat people as they want to be treated based on how they treat themselves. The best anyone will ever be able to treat you, is how they treat themselves, so if they treat themself like shit, you'll be treated worse than shit, because thats just how it goes. In some ways, morality is a rational calculation, a calculus, and it could be described in numbers, or words, or letters, but it's really just a calculation. The conclusion of it, love yourself and I'll love you.