Picardís argument is this:
PICARD: The Ba'ku. ...We are betraying the principles upon which the Federation was founded. It's an attack upon its very soul. ...And it will destroy the Ba'ku ...just as cultures have been destroyed in every other forced relocation throughout history.
DOUGHERTY: Jean-Luc, we are only moving six hundred people.
PICARD: How many people does it take, Admiral, before it becomes wrong? A thousand? Fifty thousand? A million? How many people does it take, Admiral?
The fundamental claim here is that when itís not obvious where to draw the line the only morally defensible position is extremism. He makes a similar argument for the Prime Directive in Pen Pals. Itís a lazy and destructive way of thinking.
I wonder if Picard has considered the same argument from the other direction. What if, instead of 600, it were only 300 Ba'ku? 100? 30? Ten? Three? One guy enjoying the planet all to himself? What is the magic number of people who must be living on the planet before it becomes a moral imperative to violate orders, sabotage the particle collection and sacrifice the welfare of billions in order to avoid disrupting the lives of the people living there?