Yes, he has moved very far to the right. But his work in the 1980s, and his book The Birth of the Palestinian Refugee Problem, is widely acknowledged as a significant counterpoint to official, one-sidedly national-chauvinist narratives of the foundation of the state of Israel. Morris, however confusedly and wrongheadedly, says he identified as a "Zionist" both during his more "radical" period and in his current, more reactionary, phase.
The point is not to use Morris, in his current chauvinist incarnation, to "bolster" any argument, but merely to acknowledge that one cannot necessarily extrapolate political conclusions from the mere fact that someone says they are a "Zionist". Recent academic research that shows that 90% of British Jews support Israel's continued existence as a Jewish state, and 93% of them feel that connection to Israel forms some part of their Jewish identity (i.e., that they are, in some sense, "Zionists"), but also that a large majority of them support Palestinian independence and believe the settlements are a "major occupation to peace". That someone identifies as a "Zionist" doesn't always tell us the whole story.