The original meaning of "trolling" comes from the fishing technique. It's not targeted, it's just provocation. Trolls might follow up, and target the people who took the bait (getting them more riled up, misinterpreting them, claiming they misinterpreted your point, accusing them of trolling), but they don't tend to hold a grudge. It's just a (juvenile) joke.
Harassment isn't trolling. It's goal is not provoking anyone who is un-savvy enough to take the bait, it's goal is to upset a specific person. It's harassment.
You're right that trolling means whatever people want it to (words mean whatever you think they do), but if you expand the definition "trolling" to include harassment, then it's no longer fair to say it's "just" trolling; under the assumption that "trolling" isn't a bad thing.
Harassment isn't trolling. It's goal is not provoking anyone who is un-savvy enough to take the bait, it's goal is to upset a specific person. It's harassment.
You're right that trolling means whatever people want it to (words mean whatever you think they do), but if you expand the definition "trolling" to include harassment, then it's no longer fair to say it's "just" trolling; under the assumption that "trolling" isn't a bad thing.