I feel so uncomfortable whenever people discuss the so-called "meat eater problem." Two counterarguments:

1 - This is a case of utilitarianism gone to far. Contrary to what one could conclude by applying pure utilitarianism, saving someone's life is good even if they go on to do bad things. It is not the moral responsibility of GiveWell/GHD donors to worry about how ethical the people they help are.  

2 - The conclusions of the argument are repugnant and absurd. The discussion always seems to come up in response to saving the lives of poor people in third world countries, and I have a sense that some people don't react super viscerally to what's actually being said because the humans in question are so distant from them.

Imagine this argument was being applied to people in your own country. For example, what if someone proposed encouraging doctors to go on strike in hopes that doing so would cause more people, some of whom eat meat, to die. That would be wrong.

What's being proposed here is completely equivalent to that scenario. People are proposing denying people basic healthcare - healthcare which is broadly available to the global rich - in hopes that they die and therefore don't eat meat.

Even the more nuanced proposals - such as eliminating support for physical healthcare in favor of mental healthcare - are repugnant. Imagine being a doctor and seeing two patients - one depressed and one dying of malaria. It might be okay to help the depressed person over the one with malaria for certain reasons (e.g., you only have the resources to help one and you're more likely to succeed at helping the depressed person). It would wrong to help the person with depression in hopes that the person with malaria dies and stops eating meat.

I understand that others don't want to criticize someone for how they spend their money. While I think this is a good principal in general, I don't think it applies to Buffet for two reasons.

First, Buffet controls an extraordinary amount of money. More money than anyone could ever spend in a lifetime. This gives him an extraordinary responsibility to the world.

Second, Buffet has made a promise. He said "My pledge: More than 99% of my wealth will go to philanthropy during my lifetime or at death.... Were we [my family] to use more than 1% of my claim checks [stock shares] on ourselves, neither our happiness nor our well-being would be enhanced. In contrast, that remaining 99% can have a huge effect on the health and welfare of others. That reality sets an obvious course for me and my family: Keep all we can conceivably need and distribute the rest to society, for its needs."

His promise was an extraordinarily important one - to distribute over a hundred billion dollars for the needs of society. Unless you want to argue that border militias, college scholarships, and Nebraskan politics are addressing the needs of society, he has broken his promise.