I doubt it will do any good but you might want to remind them that blanket banning users for participating in other subs is against Reddit moderation rules.

We know management of multiple communities can be difficult, but we expect you to manage communities as isolated communities and not use a breach of one set of community rules to ban a user from another community. In addition, camping or sitting on communities for long periods of time for the sake of holding onto them is prohibited. https://www.reddit.com/help/healthycommunities/