While it is true that the ability to wipe out life via nuclear detonation DOES distinguish our modern times, it is also true that humans have shown admirable (and unusual) restraint in using those nukes. Setting the potential aside, there is no escaping the fact that we are living in the most peaceful and prosperous time in human history. For those in doubt, check out economist Max Roser's wonderful graphic website http://ourworldindata.org/, where you can page through graphs of historical data measuring things like life span and global poverty rates.
Who knows whether humans will wipe themselves out? We can't speculate. But what we do have is comparative data on how the day to day lives of humans has changed for the better. One of my frustrations with WT rhetoric about the last days is that the stats they tossed around were always decontextualized. Okay, so there were 100,000,000 people killed in warfare during the 20th Century. That's a lot! But it also suggests that there were a lot of people AROUND to kill, people that would have died in childhood or early life if they had lived during other times. Numbers always have to be put within context so that you are comparing apples to apples, which is why the Society rarely offers statements as comparative percentages, preferring the shock effect of straight up raw numbers.