The difference is that the natural state of the corporation is to go extinct. Governments have so much inertia that it often takes a literal revolution to replace them.

Bad externalities are the downside to dictatorships. The externalities of a corporation are much more limited, and there is more pressure to reduce them (from governments, other corporations, and their customers).

Continuing the dictatorship metaphor, this pushes corporations to be more “benevolent”.