In the US, the principle is that everyone is presumed innocent until proven guilty. Whether what they did was right or wrong according to our (yours, mine) standards is irrelevant in a court of law...what matters is if they are convicted of doing something illegal.
Another principle of US jurisprudence is that everyone deserves a fair trial including having a lawyer, even if they can't afford one. And that the lawyer is to act on their behalf...again, whether what they did was right or wrong (or even legal or illegal). It is the basis of the innocent until PROVEN guilty thing.
And if I am in court as a defendant, I certainly don't want my lawyer deciding that what I did was wrong so he isn't going to defend me properly.
Like it or not, if the lawyers of the prosecution couldn't prove beyond a reasonable doubt that the defendant did the deed, he deserves to go free...in the US. And, no, I don't consider that evil.