This whole, tiresome, 'point' is really just a legacy of the Qur'an vs. Bible debate, which in a Buddhist context is irrelevant. Buddhist teachings are as 'authentic' today as they have always been as they are accepted or rejected on their merit and by experience of their efficacy, not solely on the authority of a particular individual. That was true even in the Buddha's time, indeed it was the basis on which he himself said his teachings should be taken.
Nobody pretends that any Buddhist text is a verbatim report of the words of Siddhartha Gautama; the initial tradition was transmitted orally for several centuries before being written down for a start. If, though, you are somehow suggesting what he actually said and, in this context, how he behaved was somehow radically different from what many millions over more than two millennia have found no reason to doubt it really is up to you to "put up or shut up".
That is, frankly, just biased rubbish I thought twice about dignifying with a reply at all. I assume you couldn't come up with any constructive response in the context of the actual debate on the topic you introduced. The suggestion that no systems of philosophy and morality have flourished and indeed continue to flourish because of the Buddha's teaching is both ignorant and absurd. Buddhism has never made any claims to be a political system. Oh, and even your comment about previously warring people is completely wrong... you 'don't see' because you can't be bothered to look.
Atheism is not the denial of God, it is the denial of the existence of God. It is also not a religion; and it is therefore meaningless to talk about atheists being 'united' or not... there is no reason for them to be. I'm certainly not 'united' with Gubbleknoucker for obvious reasons! In a different sense Buddhism is not 'united' because it simply has no reason to be. The fundamental beliefs are the same, and without being hamstrung by a need to worry about the exact words of God or a prophet, Buddhists are quite free to disagree about the details. They have never fought a war over them.
This is just plain silly. A banner 'saying' what? Like political ideologies, religions have positive manifestos and you can write those on banners, imaginary or otherwise. Atheism is the belief something doesn't exist.
By analogy, it's like comparing a group of Manchester United supporters with their scarves, shirts and banners with one guy standing in the park with a banner saying 'Soccer is boring '. Just because he isn't surrounded by a crowd of thousands doesn't mean there aren't plenty who agree with him.