Fair question. Please read on.
I don't think so. If anything, presenting non-sentients as atheists may well encourage further disregard and further unfair criticism of atheism. Even all-out insults.
But it is also intellectually honest and may help clarify and correct certain misconceptions.
I can't speak for others, but in my case I want to point out the nature of atheism as I understand it and, hopefully, also point out that there is an inherent assymetry between it and theism.
Theism, despite some odd cultural and doctrinary expectations with surprisingly good support, can't happen in a vacuum. It can only exist (or at least be claimed) once some form of god-conception arises or is proposed and there are people around with the ability to express belief in the existence of a literal form of that conception, at least to themselves.
Atheism has no such requirements and requires no effort nor justification whatsoever.
That is a fact that many apologists of theism fail to acknowledge somehow.
One of the most frustrating traits of much of the discussion between theists and atheists is that both sides often end up discussing logic and evidences with various degrees of honesty and awareness of facts, but ultimately neither theism nor atheism has much to do with logic nor with evidence.
They are both aesthetical stances, opposed and mutually exclusive but very assymetric in ambition and consequences. Theism is simply inherently more daring, all the more so when it takes the form of proselitist monotheism. To presume to decide what other people should believe in is no minor audacity.
But social reinforcement is a powerful force, and leads many Abrahamists (and to a lesser degree others) to misunderstandings on the nature and consequences of both theism and atheism. And because not all atheists are well informed, many of us end up repeating those mistakes as well.
I agree with most of what you're saying here, although in this context, it seems more of a semantic discussion than anything else. The word "atheist" would never have existed without the concept of "theism" being formulated in the first place. I agree that it doesn't originate in a vacuum; it's a product of human thought and imagination, but at a level presumed to be not possible with babies or cats.
(Of course, parents often take babies with them to church and continue attending as their children grow up, so the ideas of belief in the supernatural and theism are inculcated and conditioned into them almost literally from birth. It might not be until later in life that one develops a certain degree of understanding and independent thought to consider the possibility of non-belief.)
So, in a state of nature where such concepts don't even exist, they would lack any theistic beliefs, so they may be atheists by default, but they wouldn't call themselves that. It probably wouldn't even occur to them to call themselves something based on what they don't believe in. The term "atheist" only really has significance within a society and culture where theism is prevalent. As you point out above (and I agree with), "To presume to decide what other people should believe in is no minor audacity." If we didn't have people actively doing that all throughout history (and even to this day), then I doubt the matter would even come up. At the very least, it wouldn't be so controversial.