Without specific examples, I can't really have an opinion on whether or not the popularity of those posts were the result of brigading by any specific subreddit, or whether it was just due to regular upvotes. Usually bots will point out in the comments when a post has been linked to in another subreddit. Always happens for posts linked to by SRD and such.
If a user is following another user around and commenting on everything they do, the solution there is to ban a user, not a subreddit. Targeting a user for parody is something I believe should be allowed. For example, if someone wants to target President Bush and imply he's a sexual deviant of some sort, I believe that they should be allowed to. I don't believe they should be able to call his phone at all hours of the day and night to personally harass him, but in public places and in their own forums, they should be able to lampoon as much as they like.