Most of the pot smokers I know are conservative Republicans. Stop watching so much TV.
Two words... Bummer, dude. We of the Libertarian Party are drafting a response to this incidious proposal of yours. It is a progressive tax since mostly it is the well-off who can afford to waste their money on bongs and buds. We don't want to discourage success, so our counter proposal is to place a heavy tax on check-cashing services and upon the parents of any children who do not work in the coal mines.
If you are not serving in a public office then you have truly missed your calling.