When a judge rules on one side of an argument because of his beliefs or the beliefs of the person or party who appointed him and without consideration for the law or legal president he is an activist. The judicial appointees to the Supreme Court are a perfect example. They rule along party lines constantly.
Judges, particularly Supreme Court justices, seem to disregard the Constitution in some of their decisions; consequently, their actions should be considered activist. In light of the justices' life-time tenures, and the fact that they are presidential nominees, allows them to promote a partisan (conservative vs. liberal) mindset. As an example, the Supreme Court okayed the individual mandate aspect of Obamacare. This decision is judicial activism at its worst; it is an egregious assault on the Constitution, and an insult to all Americans.
It is my opinion that judges can be considered activists because in some instances it is their ruling that changes the social fabric of our nation. There have been hundreds of documented cases in which a judge has ruled against common practice of that time in order to create a lasting impact upon American society.
I do not believe judges can be considered activists. In many regards judges should be neutral. They should be able to look past political lines and political ideals and make a decision that is based on the most common view. I believe it is wrong for a judge to be an activist.