I'm intrigued to find out how the hell they think they are gonna be able to handle even one of the calamities, considering Netero couldn't even handle Meruem without killing himself, and Meruem was a threat level below the calamities if I remember correctly?
As far as we know - Netero was supposed to be stood at the pinnacle of nen achievement, so clearly there is something we haven't been told yet, or perhaps Beyond Netero is even stronger? He seems a bit cocky though, the strongest characters always come across more reserved and modest..