I mostly agree with you that the statement against technical solutions is false on the face of it.

How about this: if you want to prevent certain types of discussion and interaction in an online community, the members need to have some kind of consensus against it (the "social" part of the solution). Otherwise technical measures will either be worked around (if plenty of communication can still happen) or the community will be damaged (if communication is blocked enough to achieve the stated aim).

Technical measures can change the required amount of consensus needed from complete unanimity to something more achievable.

In our case, we may not have had the required amount of consensus against feeding trolls, or of what counts as a troll to avoid feeding.