Mercy doesn't teach the person who has done wrong as lesson so therefore is as a greater risk than someone who has been punished from their wrong doings. People who have been punished for their wrong doings learn from their punishment (majority of the time) so therefore are are more likely to not do it again whereas mercy doesn't teach that person anything.
Guy: Hey, guess what? I just killed someone!
Judge: Not pressing charges, because we have mercy.
People: Sweet! Now we can kill people and get away with it!
If there was no justice, we wouldn't have laws, and there would be an anarchy. Does anybody else sees the problem here?
Justice is the pillor of society, if government can't provide it , its noway should called society
Mercy should always comes second to Justice.
Mercy can only be given by GOD, So its better we talk about justice here.
But keep in mind that ...
Justice cannot be for one side alone, but must be for both.