Sex offenders, by definition, have committed a crime. So that's not really a pre-crime list. Although, sure, some people may not belong on those lists, and it's pretty life-ruining for them.
Your point reads a bit like this: "These injustices exist that you should be against, so why are you supportive of them?"
No fly list in particular is an abomination. That said, given that Delta is creating a its own version ( and asking other cartel members to join ), soon we may be revisiting this conversation.
It's like seatbelt-laws, yes, they infringe your personal liberty to do however you pleases, but they also generally help to reduce accidents and, implicitly, reduce cost for society (and not just in terms of money).
Again; from my outsider-point-of-view, that the US even has to have these kinds of discussions seems so weird to me. There are way too many people dying in the US because of the absurd amount of guns, not trying to address this with legislation (as every other advanced nation managed to do) seems outright absurd.