I would ask lemm.ee users to please use the report function whenever you see our rules being broken in any of our communities! A large volume of rule breaking users from a single instance would certainly push me to defederate that instance, and reports would be the main signal for me to gauge that.
I don't have the capacity to go out and vet content on other instances in general (as all admins, I am running lemm.ee as a volunteer out of my free time). I want to be upfront: I am not providing a curated service in terms of who we federate with. This is why I wrote todays post about administration and federation on lemm.ee. So please bear in mind that as a user on lemm.ee, you are expected to share some responsibility for keeping our communities clean, by always downvoting low quality content and reporting rule violations. In addition to downvoting and reporting, I personally also am a huge fan of people who have the energy to respond to bigots, explaining why they're wrong (in civil terms) - even if there's 0.001% chance of getting through to the particular author of a horrible comment, there is still a chance that a rebuttal in the response will be seen by someone else who will be affected in a positive direction.
To be clear, I am not somebody that believes that all ideas should get a platform without exception. Quite the opposite, I am super happy to shut down hateful content. It's just a matter of putting my energy where I think it is most useful. For example, I would rather spend a week worth of free time working on better moderation tools or better self-service tools for users to curate their own feed, than spend the same time going through external instances in order to figure out how many racists they have and how well are they moderating them. That is why I have made the decision (for now) to focus most of my moderation efforts on things that happen within lemm.ee, and not externally.
I also want to say that I do not want to act hastily based on little information. I'm sure this will frustrate some of our users (and I'm very sorry about that), but I have not had time to research the Exploding Heads situation, and I don't want to effectively create a new rift in the federated network, without first being absolutely sure that such an action is really necessary to protect lemm.ee users.
By the way, regarding this the_donald situation on sh.itjust.works, the OP of the linked post said this:
Since The_Donald was removed, I did not find more racist content on the mentioned servers. That is part their tactics.
This seems like a great outcome to me - the_donald was removed and there is no more racist content. I would not think this is a good example of a reason to defederate another instance. I understand that part of the complaint is that the admin of sh.itjust.works took too long to respond to the situation, and as a user I can see why this would be frustrating, but as an admin, I can tell you that I can also see why he wanted to see evidence before acting. In the end, I really like that he removed the community as soon as he saw evidence of it being awful.
Just to leave you with my main point, I do not want to federate with instances which aim to hurt our communities or users, but I need concrete and specific evidence of this before I take drastic action. So please report rule violations, and if I see that banning violators does not work, then defederation will certainly be the next move.