* They realize it could be used for bad in the future, but they have delusions of, "bad things couldn't happen here." [ Sort of like the idea in America that, "Fascism could never happen here." ]
* They are more comfortable with creating said power because they are currently in control of it, and are short-sighted enough to not realize that this won't always be the case (i.e. the 'government' will control it, but they aren't guaranteed to be a part of the government).
Another possibility, avoiding Hanlon's razor: They honestly have trouble understanding how or why someone could in good conscience disagree. They don't want control or censorship in the abstract; they just want to legislate morality on this one issue because their position is so "obviously" right. Using laws like this to censor things that don't harm kids would be unthinkable, but harming kids is clearly bad, so this law neither is nor opens up the door for censorship. They don't see the slope because the motives look completely different.
They're not ignorant to the outcome here - it's exactly what they want and has been planned that way.
This is a serious fucking power grab.