I understand that the president's perogative to commute a sentence, offer clemency or a pardon is as the article describes "a one ticket ride."

But why should any member of the government be allowed to abdicate the government's responsibility to treat all citizens equally? If Libby, why not Rita?

Pardons, clemencies and commutations that are granted to one person should apply to all people in similar situations.

There aren't any "similar situations." There are similar convictions and similar sentences, but the circumstances surrounding those are all very different.

Because judges and legislators do stupid things. Sometimes it is the fault of one of them; other times it may be both. Remember the much publicized kid with the french fries on the DC Metro case that Roberts did? Roberts followed the law which was written by Congress (Congress writes the local laws in DC). No doubt some person or persons stained their thousand dollar outfit on the Metro from some food. As a result they retaliated by passing a stupid poorly written law. Roberts merely followed it.