Quippy but untrue. "Not golfing" doesn't have news articles, blogs, apologetic tomes, influential figure-heads, social gatherings (online and offline), charitable organizations and all sorts of life and energy-consuming efforts dedicated to it.
Atheism is indeed the religion of man, who has set himself on his own throne, denied the existence of a Creator, and crowned himself god - deciding that HE will be the arbiter of right and wrong. The same forms of worship (investments of time, energy, money, etc) that can be devoted to the Divine are simply channeled inward in a self-righteous pursuit of independence.
Most organisations promoting atheism tends to explicitly associate with ideologies that sometimes pre-suppose atheism, but are not just atheism, such as humanism. E.g. the biggest "atheist" organizations in most countries tends to be the Humanist Associations.
To the extent that there are organizations etc. "just for atheism" rather than humanism, this tends to either be tied to ideologies that either encompass just small parts of atheists, e.g. "hard" atheists who express absolute certainty in the non-belief of God, or "radical" atheists who see theism as actively damaging and something to be fought. Those you could very well consider ideologies.
Another category are groups that band together not over atheism per se, but against religiously motivated discrimination, but most of these tends to focus on secularism, not atheism per se.
Calling atheism itself an ideology because of any of the above is ascribing far more to atheism than is actually there.
Saying that there are atheist ideologies where the absence of belief in a God is an important principle is true. But atheism on it's own is the simple absence of belief.
If people who didn't golf were considered subhuman and needing of "saving" then non golfers would develop a supportive community too.
Please don't confuse "community" with "religion." Bronies also have those things you mentioned but not a single person would classify being a Brony as a religion.
Same with ideology, not all ideologies are religions. Believe that the Earth is flat is an ideology but not a religion even though personally having that ideology may be based on religious beliefs. Same with veganism.
