You define the judge by what he "often" is, or may be. Is judicial activism therefore appropriate if the judge is not a "corrupt political hack"?
A judge must view a law as written and as intended by its writers, whereas a jury of peers can determine if a law is bad law or is simply inappropriate in a certain case.
According to whom? Where are the roles and limitations of a judge or a jury defined?
“I would rather be governed by the first 2000 people in the Manhattan phone book than the entire faculty of Harvard.” — William F. Buckley Jr.
Similarly, I trust a jury of peers before I trust a judge or a lawyer or any legislative body.