Even if you use the fishing definition...
fish by trailing a baited line along behind a boat.
It still inclines that there is a motive to capture/ to lure/ to hook something. It is never in a fish's interest to be hooked by a fisherman. Best case scenario they are wounded then released while worst case is they end up as dinner. Therefore, even by a fishing definition there is intent to harm.
Trolling by any definition has some negative motive.