Even though Ashton said that he will try to think of a way to help with this calamity they're about to face, his friends weren't so convinced that he could do something on his own.
This isn't them questioning Ashton's abilities or resolve. It's just that the situation was far too volatile that they didn't think that a single person can contain it.
That being said, they're a bit helpless too.
Nobody could really say that they will be able to handle a Black Fog well. Hell, none in the generation even encountered one except Ashton. And Ashton certainly didn't confront, he hid instead, that's how he survived.
So knowing this, the likelihood of him concluding his claim was extremely low.
Nevertheless, something must be done. They couldn't just sit still after knowing this. A lot of lives are at stake. Humanity as a whole was being threatened by this disaster.
