As I said yesterday on the Baby Boomers and booze thread,
Nobody "owns" the contents of a thread they start, although it can be frustrating if it is derailed especially early on
Yes, it can be annoying if a thread started in good faith goes off at a tangent, but unless this is done deliberately to "high jack" a subject that's how discussions and conversations develop. If someone is being deliberately contentious or obstructive I suppose GNHQ might step in but otherwise you have reached the correct conclusion in your final 2 lines.
Mind you, I think the poster with the antisocial neighbour felt miffed at how that thread went,(!) but to reiterate
nobody owns a thread