I think the trashing of a thread by deliberately introducing totally off topic items should be prevented. There is no compulsion to post on every subject. Thread drift is inevitable. But I think anyone can see there is a huge gulf between drifting a thread and deliberately sinking it.
Sabotaging is a brand new game developed by several childish posters who have the mistaken idea they rule the roost and make up the rules.
If everyone behaved the same way the fourum below the line could no longer function. It takes zero skill to introduce a new topic in a thread and it can easily be crafted to target specific people. These same people are the ones to start shouting "not fair" when they and their little ruses are mocked and ridiculed.