In paragraph 5, the article most likely highlights Democratic Senator Robert Byrd in order to show that

in impeachment proceedings in the U.S., politicians may stand up against public opinion.

in general, the real motives for a presidential impeachment in the U.S. have nothing to do with concepts of fairness and justice.

a politician taking part in U.S. presidential impeachment proceedings may put party loyalty ahead of personal beliefs.

the question of whether or not President Bill Clinton actually did commit a criminal offense was never an important factor in the impeachment proceedings.