Just to restate: I’m not saying we don’t act selfishly. I sure would. Let’s just not pretend we’re being altruistic.
For all I know a flowering plant will develop a brain and become sentient in the next 200 million years.
I guess they prefer to take an extreme Darwinian view. Since complexity is not the goal of life, merely a side-effect, there is no life on this planet that is more advanced than any other. Assuming a single abiogenesis event, all extant life has been evolving for approximately 3.8B years.
We may choose to think of brains, and our human brains in particular, as the bees-knees. Objectively, they are not though. Just one of many successful branches of the tree of life.
Consider that our brains are the only organ on the planet that is able to understand the concept of life, reason about itself and all other life around it, understand the concept of evolution, and even conceptualize time billion of years into the past and future.
Not all life on this planet has evolved even though it had the potential to do so.
If we attribute "advanced" as evolutionary steps rather than the inaction of simply existing then clearly we are more advanced than a bacteria. However I will concede your point for other multicellular life.
Here is where words like "narcissism" tend to land. It isn't personal against yourself, so please don't take offence. It is a philosophical viewpoint that is often stated, but appears to lack evidence. I don't have any counter evidence, but I strongly suspect it to be factually incorrect. And I believe the burden of proof is on those making this claim.
Further, even if we allow the above claim to pertain, this position makes the strong assertion that the very qualities that modern humans are uniquely superior in, are the very things that must be held uniquely special. To some of us, this just seems circular and too convenient.
Is it more likely that humans hold such characteristics to be the epitome of success because there is some objective model of success to which we alone conform (e.g. conceptualisation)? Or because it merely suits us to do so? I believe the latter, though you may disagree.
Feels like the brain might be a little biased when it thinks that the brain is the greatest form of life to ever be created :)