Mozilla (and Eich) decided that this expression from the community was sufficient for Eich to step down as CEO. No one forced them to do it, much like no one forced them to make Eich CEO in the first place.
This is exactly how public dialogue is supposed to work. If you find that a particular executive at a company has taken actions you disagree with and this upsets you to the degree that you wish to stop using their products, you're free to do so. You're also free to talk to others and encourage them to do the same. The company is free to retain that executive or remove them depending on how they feel about the public outcry you've raised.
This is free speech and public dialogue. It's people deciding what products they want to use and talking about it. It's companies deciding what to do based on what's good for them and their objectives. Which one of those things do you object to?