What do you think is the stupidest wrestling rule? Mine would have to be the old removing a turnbuckle pad and throwing your opponent into it is an automatic disqualification. So you can throw your opponent into the ring-post, the announcers table, even the steel steps, yet they are all OK. However, you are DQ'ed if you throw your opponent into an exposed turnbuckle.
Those other things are considered hazards that are part of the normal ring, though. By exposing a turnbuckle you're creating a hazard that isn't covered by the normal leeway of the referee and thus it's a DQ. Plus it's not "OK" to run someone into the ringpost, there's actually been many times where someone has in fact been DQ'd for doing it. Not consistently, but technically it can be one.