Not all legalization supporters are even pot users, much less pot addicts. (I'll take this opportunity to mention that pot is less addictive than alcohol.)
was that the government could regulate and tax it. Now they are bitching about it.
Even if it was the same people in both cases (for which there is no evidence on the table) they may simply have overlooked the possibility that Washington would OVERtax and OVERregulate.
That is correct. They can only tax it to the point that is makes economic sense to purchase it legally, otherwise people will turn to the black market.