This basically opens a whole new can of worms. If you want to ruin a projects reputation, say they're your competition, just hire a bumping service on their behalf and soon they'll be tagged as cheaters or at least shady.
Something to consider anyways
I guess there is a chance for something like that to happen ( highly unlikely imho), but but even then OP can report those spammy posts and mods will delete them, or in case of Minereum he can delete those posts by himself, as their thread is self-moderated, and it seems that he is not doing that.
Most of those altcoins are so bad that they don't even need some external enemy, their own incompetence and delusion are more than enough.