It all depends on how much time you want to consider. The past few years? Then sure, you're right. The 20th century was incredibly violent right up until its end, so it should be hardly surprising that the 21st is mild in comparison (so far).
Not to mention, that, if we ever wanted, we could, at any point and time, effectively destroy our planet in under 2 hours. At no point in human history have we been able to achieve that.
In addition, technology has led to an increase in fighting capabilites of a single soldier, thereby reducing total soldiers needed for battles and reducing death tolls. There's also been an extreme increase in medical technologies and advances in societal structure(slavery for example).
Are we less violent? No, we still have the same urges as we have through out history, but we've put into place, our own safeguards to prevent us from unleshing our truly violent impulses. (Look at the EU v US stuff on this forum. Many years ago, this would have been grounds for aggressive negotiation or expansion, now it's a monetary and influence war that tends away from the violent extremes.)
But, all it takes, is one person, one single person with the will to do it, and the world can burn quicker than we can blink an eye.
Also, we've developed the capability to create bio warfare, if we so wish. The amount of weapons in our arsenal to kill 1 billion people(more than probably most wars killed between 1700-Present) is just a button away.
(I am not agreeing or disagreeing, just stating that never discount the technology that allows the us to say we aren't as violent, from being used to make us the largest mass murders in history.)
