It sounds like an overreaction.
It's not, it's about showing that you can't just go around and willy-nilly delete entire off-topic threads because someone (you) doesn't like it.
You might not care that your contributions get deleted, but others do. That could force otherwise good contributors to the forum if they know entire threads they contributed to will be deleted.
Hence my point that you either make it policy to remove them all, or you don't.
Sure, under exceptional circumstances an entire thread could be deleted. And this actually happens a bit if the thread is new and not people have responded.
It sounds like you don't share my opinion of it and are content to keep it. It's your forum, your call.
I have not read the thread. I can't go around reading every single thread from scratch that people complain about. Easier to just lock them i there are too many complaints.
I'm sitting in my hotel room now on a family holiday and here I am having to deal with this. Want the job?