A) he has sold a good portion of it. B) Berkshire Hathaway is a holding company. It is diversified already. So there is much less of a need to sell it.

So you're saying Berkshire Hathaway is much better setup as a long term business than Facebook; therefore a better investment. I don't disagree at all.

No, being diversified doesn't instantly make you a better business. But it does make you a safer investment.