The point is that Sergey has many "public good" issues to choose from. Some issues will have far greater impact on relieving suffering in this world - especially for those who have little or no voice themselves. Some issues will have a much smaller impact, especially for those who already have a lot of power and are wealthy and very vocal about their issues. Some issues will be very divisive among Google shareholders and users. Some issues will be very uniting.
It's really a matter of choosing what to do with your resources - and Google is a public company now - not a privately owned company by Larry and Sergey. Employees and shareholders are on both sides of this issue - what may be 'obviously the right thing to do' for some of his shareholders is 'obviously the wrong thing to do' for others. This is a divisive move for his company on an issue trying to help already very powerful and wealthy advocates. To spend brand capital so heavily and unilaterally like this when you could be doing so much good elsewhere and at the same time build unity among shareholders and strengthen your brand - just seems like a poor decision.