so nothing can be done about bots posting near instant and often off-topic responses to every single one of Trump's tweet? not that it bothers me the slightest, but I find it to be a concerning case of double standard given all the allegations of Russian interference on social media.
You're comparing unrelated "standards". The case isn't about the health and well-being of social networks, but rather about whether the actions of government officials on those networks qualify as "state actions", which are required to comply with the Constitution, or private actions, which aren't.
This changes nothing for mechanisms trying to prevent bots, or really any other management of posts.
The only requirement is that such mechanisms must be viewpoint-neutral. So you can, for example, shuffle all replies in the first minute. You just cannot penalise only those mentioning cheeseburgers, or democracy, or using all caps, etc.
> so nothing can be done about bots posting near instant and often off-topic responses to every single one of Trump's tweet?
Lots of things can be done about without violating the rule at issue here, but the thing that cannot be done about them is Trump selectively blocking them based on disagreement with the expressed ideas.