Divisions within the left, such as that which has occurred in Respect, always have their basis in political disagreements. Socialists must always fight for their principles to take the movement forward.
Few things are so distressing for the socialist left as the bitter internal disputes marked by personal diatribes. Such disputes are not unique to the left. Witness the interminable rows within the Tory party, or the decade long feud within New Labour between bomber Tony Blair and bomber Gordon Brown. But the socialist left is based on principles very different from today's mainstream parties, and people expect better from it.