I think “gray” (or “centrist” or “nuanced”) classifiers are often used as a way to shield a position from criticism while not really engaging with it to any end. This is the “gray” position that you might see discouraged.

The “gray” that I often see encouraged engages with the entire complexity of an issue. It follows the issue to its roots and at those roots interrogates them to their conclusions, establishing for each a black or white position. In aggregate, these conclusions might not fall neatly in line with an existing black or white position.

An example might be the war in Ukraine. You may simultaneously feel like Russia is being imperialist by annexing parts of Ukraine, feel that Ukraine has a fascist sect that should be eliminated, that Ukraine is right to self-determination, that it is unfairly positioned as a proxy pawn for NATO to exercise its power, and that the war is being drawn out to force national pressure on access to oil, that the historical recognition of a regional ethnic group should be respected. Taken to their ends, these positions do not land fully in support of either side in the war in Ukraine, but each facet requires interrogation and is owed a decisive stance.

If you’re putting in the intellectual work, then gray positions (as the aggregate of more decisive positions) are fine. If you’re not, and you’re just washing your hands of engaging with issues. “centrist” positions are even more dangerous because they are not defined by beliefs, but rather relative to others’ beliefs, allowing them to shift without ever consciously forming any opinions.

tl;dr: gray fine, ignorance not fine.