"has existed long before humanity" isn't relevant for my argument.
"Will exist long after humanity" -> maybe, maybe not. If we're smart, capable and humble enough, we could, in principle, intentionally outlast them.
By "intentionally" I mean: we can design our future lightcone such that, by whichever measure you care to choose, there are still humans around. Yes, bacteria could be still around, but it won't be because they _chose_ to be around, it will be because it just so happened that the universe arranged itself in a way that they are still around.
By "in principle" I mean: if we spent enough resources, energy and smarts and built a civilization around this goal, we could plausibly (given the known laws of physics) do this. Whether we _will_ do it or destroy ourselves first any of the possible various means, is an open question.
Lineages of bacteria that exist today, here, will only keep existing in the _far_ future (billions of years from now, after the sun chars Earth and then spends its energy budget) if it just so happens that a panspermia event kicked some off our solar system and then they just so happen to find a suitable solar system to keep existing.
The problem with that argument (which people also use on animals like sharks) is it assumes that these other organisms haven't also been evolving in the human timeframe. Yes, you can find evidence of organisms that look more or less like modern bacteria or sharks long before humans existed, but the idea that these organisms haven't been under selective pressure since is false. Indeed, they are probably under greater selective pressure now due to the effects of humans on the planet.
Bit of a ship of Theseus situation I suppose. Humans have been and will continue to evolve as well, but you still want to credit them as "humans", so why not give the same logic to the bacteria?
