Are the angry at the right thing? Being angry at the religious doesn't further the atheistic cause, it only hurts it.
Lets see here... Lets take a little trip threw secular history.
The Greek of course being the acceptation, most religions were fully intolerant of anyone who believed differently, the Jews have orders in there book to stone nonbelievers. Typically stoned, burned, and otherwise murdered.
Now a little closer we have Shakespeare times, William had a book with an atheist as an antagonist. At the time, atheist virtually meant "Godless and immoral". Before that time as well as around it people who didn't believe were still shunned.
America's founding and the revelation was done by people of several religions and they were rather tolerant of religion at that point. Major point in history, not being able to kill people who don't agree with your religion!
Now lets get closer to the modern time, to who was one of the first "angry atheists", Mark Twain. Samuel Clemens. A very vocal atheist for that time, he wrote several works against religion including
Letters to the Earth. I am not sure how he was taken by the general public, personally.
Then there was the cold war, were America used our foolish assumption and made atheism an enemy, much like modern people are doing with Islam. Except well atheism wasn't the driving factor or any factor of the Russians. They simply had a different religion(being none) and America demonized it, adding officially the "In god" things.
Finally, modern times! The invention of the internet seems to be killing religion, Thunderf00t has a decent video if you want to watch on that. Britain is secular now. Now, it is OK to be an atheist in some places! The "angry atheists" are also visible now. But being an atheist is much easier than the ancestors had it, now there are atheist forums. Atheist groups. Atheists actually have a say in how things work now! For some reason we did not have that when we were silent. Things will continue to get better, as long as at least a few atheist remain "angry" or at least "militant". I personally prefer the term "Aggressive", it sounds cooler.