It's a change in the mindset. And it can begin as small as stopping a bully. Where they normally would get away with violence. It probably starts with bringing up children. There are a lot of children that learn only to obey, obeying is good disobeying is bad. Well sometimes disobeying is very good, the right thing to do. But if you are brought up with obeying is equal to being good, then the moment you get orders to do bad things you will not think, but just do as your told. This is the danger.
("you" is not you personal of course.)

My grandparents disobeyed the nazis in the second world war, I think it has shaped me unconsciously, and made me question a lot of things about wars, governments, tyrants, authority in general.
That questioning finally let me here. Questioning everything is a good thing i.m.o. Also questioning authority.
Questioning everything is skepticism. ;)