I like to browse All as well and haven't noticed that bot. If the issue is just with a single account, I think defederation seems unnecessary. Could you provide more information on the benefit for defederation versus banning the bot on Lemmy.ca? And I'm one of those people who prefer pledging defederation of Threads, so I support such a move depending on the situation.
EDIT: Correction, I checked my block list and that user account is in there. 😂