I think you should respect his choice, but we can argue about the reasons and argumentations for that choice.
I don't know if Mr. Stallman has siblings. But if not, it means that his bloodline will end with his death. Let that sit for a moment and think about it.
Think about the hundreds of people in your ancestry that lived through world wars and the dark ages and all kinds of other "bad times," compared to the hundred or so years we are currently living in so that you can make a choice to end your bloodline for good.
While he has some pretty compelling reasons, he also potentially denies humanity not only the best version of himself and his values but maybe one of the greatest minds of their time. If you don't have kids, you'll never know or see their real potential.
I personally think you owe it to the people who went through pain and hunger, slavery, world wars, and all of the kind of other terrifying things that we can read up in our history that you keep the bloodline going.
So while I respect the choice he made, I wouldn't necessarily call it clever for a man with his intellect.
It is only one thing for sure and that is egocentrically and selfish. On the other hand, if he truly thinks he has nothing of value to pass down the line, be it genetic material or his values, then it is a good thing he decides to have no kids.