How much input does/should the OP have in controlling a thread?

I’ve seen this attempted and failed. I’ve seen a GD thread where the OP basically disallows disagreements and therefore the thread was locked.

Ah… Here we go. Searching GD shows this recent thread:

This led to a modnote that stated that the OP essentially wasn’t interested in a debate:

And it was eventually closed, because as stated before, the OP basically didn’t allow there to be any real debate.

So while your concern is valid, that tactic isn’t allowed on the board and ultimately won’t work.