Yes you’re right about public image and a company wanting to preserve it. And I might be a little hyperbolic about what I’m saying. But really if it was just public image along with their ads, they would delete/(stop using) all of their accounts to show that they didn’t want anything to do with Twitter as long as they had hateful content on there.
With or without people monitoring twitter you’re still get that type of content on any platform. You can only reduce the chance never completely stop. The point is you would have to be in those groups following those feeds to see that content.(allegedly) If it took Media Matters having to follow those groups for hours and then following Disney or any other company to show that, then twitter is working to make it harder for that to happen. If this is about a company’s image, even if a Nazi account would happen to see ads in their feed unless they were out her telling you, you would be none the wiser. I highly doubt if they did the same thing on any other left lining platform that towed the line, would there be the same reaction?