I don't think anyone said Bug was an auto-win against any other types (except for Mega Pinsir vs Grass). It's simply dominating the metagame in a way that we don't think is healthy.
I'm willing to wait one more month until we see August's statistics before we decide on a Bug nerf (it's ultimately the Council's decision anyway), but if Bug's usage keeps going up or if it even stays at its current level, we need to do something about it.
Why again? You should let players figure out meta trends on their own rather than banning stuff every 2-3 months. Flying dominated the ladder for almost half a year until the Zapdos ban and it was pretty clear that core was almost untouchable (Greninja said hi but banned lol). You should understand that "promoting diversity" =/= "equal usage distribution". People are gonna use whatever they feel it's easier/more fun/cheaper to ladder.
(I feel like Ghost is pretty underrated for example. It has a nice balance/stall team that deals with a lot of mid tier/upper tier types)