There is no real explanation for why the pledge is "bad" except for the tired argument that the state is good and private foundations imitating the state are bad . There is no further clarification or explanation; We are supposed to accept this as some sort of given, without pretext or afterthought. Articles like this are bad .
Private charities have on average been terribly inefficient in the US. However, in terms of Conspicuous consumption ( https://en.wikipedia.org/wiki/Conspicuous_consumption ) they are better than building ever larger boats.
But you gotta spend money to give money!