> Eg. The lack of opposition to the idea that water is wet does not imply that water is in fact dry and everyone is just brain washed

There's no world in which no opposition actually exists when there is a little bit of freedom. You can observe it even in small groups where people can express themselves: you won't have a single convergence of opinions on every topic.

There is in fact quite a lot of opposition to the idea that water is wet. Just Google 'is water wet?'.

Theres no way to know if they have considered the alternatives, because it is illegal to even present or discuss any alternatives, and illegal to ask them about it.