If you have time, read Steven Pinker's book, the Better Angles of our Nature, which deals with the decline of violence over the centuries.
Generally, the world is getting BETTTER than yesterday. You can point the following facts:
- The violent deaths (by war and crime) are lot less in the last 50 years than any other time in the past! We're talking about relative deaths, i.e. deaths as to the world population. 20th century wars claimed less lives/world population than the wars of the past centuries.
-Diseases? The 20th century deseases are NOTHING compared to the past centuries. The Spanish flu was nothing compared to the Plague of 14th century. Modern medicine has eradicated/reduced significantly most of the diseases that plagued humanity for thousands of years.
-Greater life expectancy, greater quality of life, decreased child mortality rate, and lots more.
You may use an illustration(jws are illustration junkies): If your JW believes we live in the worst era ever, you may ask him "In which era would you rather live if you had a choice, then?" What can he answer? None. Because we live in the best (or less worse) era of mankind since its dawn. If you lived, let's say, 300 years ago in Europe, this is what your life would have been, in average: You would be part of a family with 10-15 kids, most of them who would die in infancy. If you were so lucky as to survive, you would spend your childhood and your entire adult life working from dusk till dawn like a dog, every day, in misery and semi-starvation, and would be lucky if you lived more than 40 years. The most probable is you would die between 30 and 40, due to a combination of diseases, fatigue and ill-nurishment. And THAT era would be better than ours??