Woah, time out a second.

Think about this for a sec pisshead. Sure, it's another law that takes away your freedom but it's just another law that noone will obey.
Chances are anyone in your vicinity when your talking about cannabis will be safe enough to let it go. This doesn't necessarily mean EVERY time someone hears drug talk they will stalk you to your address, write it down and take it to the cops. If anyone cared that much about drugs in society, they'd report you anyway for advocating their use, policy or no policy.

People arn't going to live in fear for the rest of their lives knowing they didn't tell PC Plod about those guys making marijuana jokes on the train . People will fuck it and acknowledge how dumb it is. What do you say when a cop asks you if you knew about some guys buying drugs?

You say "no".