JMO:
I think disagreeing about issues on a message board is def. not stalking and holds no legal liability.
On the other hand, I think posting untruths about someone (for instance claiming they are a pedo or something) could be actionable in civil court (libel)....but if the person brings a defamation case they are opening themselves up to having all their dirty laundry uncovered and aired.
Also, if someone takes harrassment into real life there is a possibility of criminal charges as well as civil retribution.
Suing someone is a huge pain and very expensive...normally it wouldn't get that far...hopefully.
The situation I am thinking of involves a complete nutbag who basically says they are going to sue people for stalking who disagree with them.
Just wondering if that has any legal basis whatsoever....