We remove rights all the time, because bad people do bad things. You have to follow road rules for example, you are not allowed to buy components which could be used to build a nuclear bomb, all countries restrict access to weapons (they just draw the line at different places).
So the argument that we should never use "the terrorists" or "the children" to make policy decisions is overly simplistic. I believe the sort of reasoning is actually counterproductive. Even here on HN many believe a restriction on crypto currencies is justified if it curbs tax evasion, in other words they believe the trade-off between right restriction and societal benefit is worth it. So arguing that we should never use "the terrorists" to argue for restricting rights is very obviously contradicting how we are implementing laws, so it is not convincing. Instead we should argue why the trade-off is such that the argument does not hold in this case.
So the argument that we should never use "the terrorists" or "the children" to make policy decisions is overly simplistic. I believe the sort of reasoning is actually counterproductive. Even here on HN many believe a restriction on crypto currencies is justified if it curbs tax evasion, in other words they believe the trade-off between right restriction and societal benefit is worth it. So arguing that we should never use "the terrorists" to argue for restricting rights is very obviously contradicting how we are implementing laws, so it is not convincing. Instead we should argue why the trade-off is such that the argument does not hold in this case.