But Google has no intention of doing the right thing anymore than Microsoft or Disney does. These are corporations and their executives HAVE to do what they think will be best for the corporation. Not what they think is best for mankind.
This is how for profit businesses currently work. And PR saying anything to the contrary is simply not true.
Corporations are run by people with a complex set of motivations and constraints in which they make decisions. Some of them make decisions with intent to harm. Some make decisions with intent to help.
No one person is automatically turned into a ruthless amoral person just be being employed at a corporation.
They can quit. They can speak out. They can organize. They can petition for change. They could join the more ethical competition (if one exists), or start their own.
This is especially easy to do for employees of a company like Google, with excellent job prospects and often enough "fuck you money" to do whatever they want without serious financial hardship.
They are not hopelessly chained to the corporate profit machine. They can revolt -- that is, if their morals are important enough to them. Otherwise they can stay on and try not to rock the boat, or pretend they don't know or are helpless to act.
A handful of Google employees chose to act and publicly express their objections. This action got results. More employees in companies which act unethically should follow their lead.
Ultimately, though, I agree with zaphar that you are overgeneralizing, since corporations are controlled by humans -- executives, other employees, and shareholders -- and human motivations can be complex.