Marcelo Glesier is wrong for another reason. Atheism and agnosticism are not mutually exclusive. Atheism is a stance on religion, specifically a disbelief in gods. Agnosticism is a stance on knowledge, specifically that we can't know anything about gods. It's possible to be an agnostic-atheist, which is the stance that, there isn't enough evidence for the existence of gods, therefore the logical thing is to not believe in them.
One can be an agnostic-theist, "There isn't evidence for God, but I'm going to believe anyway."
One can be a gnostic-theist, "I know for a fact God exists, that's why I believe."
Glesier's argument is a criticism of gnostic-atheism, which is, "I know God doesn't exist, so I don't believe." As the article points out, this stance can be reasonably applied if God has a clear definition. The God of the Bible is contradictory, and can therefore be easily disproven. Some idiot walking around claiming to be God can be easily disproven. Gods of different religions that have conflicting natures can be disproven, since both can't exist at once. God as defined through fallacious logical arguments like the Cosmological Argument can be easily disproven.
Aside from that, any given theist is still an atheist towards all the gods of competing religions in which they were taught to not believe.
Yes. Just as you say. Except that the arguments tend to be more about the labels, than anybody's actual state of non-belief. Over the years, I've done my own field testing.
When I used the Agnostic label, both believers and Atheists wanted to know -- What would it take for you to make up your mind? I know what the word means. That's not how it was received. In general, it's taken as wishy washy sitting on the fence.-- I was told to Grow a spine. This is the basic argument that Agnostic provokes. It gets old fast. In general, I did catch less hostility than the Atheist label.
Sitting on the fence is a common refrain. Mr. Deity/Dalton said -- "You could totally lose a nut that way."
A few years back, I joined a few Atheist groups on Facebook. The same question kept coming up, as though for the first time. If you had to -- gun to your head -- choose a religion -- which religion would you choose? I said, Agnostic. I thought it was funny. From the response, you would think I had walked into their church and pissed on their altar. I had to drop out. These groups had no sense of humor at all. The last time I looked, they were all gone. Small wonder.
It's not as true now as it used to be. Still, saying Atheist brings out the hate. And the fear. Sometimes, a really irritating curiosity. One day, I'm shopping at the local grocery. A woman that I had talked with earlier -- I had taken a class with her -- walked up to me with her roommate. She said -- This is the Atheist I was telling you about. You would think she had found a Bigfoot. Other memories cling. The odd party where the topic of religion would come up. When asked, I said Atheist. Out of no where, I would be asked -- Can't we all have mutual respect?
For me, the real problem with saying Atheist, is the stupid metaphysics arguments, that result. We all know them. I won't list them here. I am so tired of metaphysics. As far as I'm concerned, the only time to turn to metaphysics -- is when Prune juice and the other physics, fail to produce a movement.
I also tried Pantheist. It's amazing, how many people can't tell the difference, between Pantheist and Polytheist. I would be asked why I believed in the old gods. Or I would catch a lecture on false gods. Like there's a difference between the false gods and the real gods.
The real problem with Pantheism, is that it's dishonest. If everything is God, then God is nothing. Of course, there is no reason to invoke the God idea at all. It's simply a way not to say Atheist.
My favorite label, these days, is Apatheist. Not caring about Theism. There is not knowing, which is Agnosticism. Not believing, which is Atheism. And not caring which is Apatheism.
It's an end to arguing. Even if God could be demonstrated to exist -- it still doesn't matter. A deity which neither helps nor hinders, has no relevance and can be ignored.