Not all social media bots are malicious. And not all social media bots are posting content from low credibility sources.
A good argument must imply that social media bots are a net benefit to society and democracy, not that some good ones exist.
The collateral damage from banning them all may be worth it, if they're a major means for pushing low credibility content and disinformation.
The idea that AIs (broadly defined to include simple bots) are net more trouble than they are worth has been kicked around in literature forever. It’s fun to live in the age where we get to wrestle with it in practice.