Clearly, the sentence you quote is making an unqualified absolute statement, which are usually easy to pick apart and tear down. After reading the whole philosophy, I'm not really sure what they mean by "guarantee" and "pointless" here. I doubt they're saying that all programming in "unsafe" languages is "pointless."
I suspect they could just reword that sentence to say something more clear. E.g. what kinds of correctness they weigh most heavily. Does Pony protect me from all classes of all possible bugs? No? Because that is impossible? Agreed. Then which kinds of bugs?
Just before, it also says: "The Pony philosophy is neither “the-right-thing” nor “worse-is-better”. It is “get-stuff-done”." This is admitting some sort of balance is being struck here...