Fireflybob,indeed not everyone in the UK has smoked cannabis or is in favour of its legalisation. However its use has been prevalent for at least three decades. Nearly everyone under fifty who gets out a bit, surely including yourself and your teenagers has been 'exposed to cannabis' haven't they? Quite normal people, that you know, have used it and don't take kindly to being branded as criminals or a danger to society. Most of the rest can see that their user acquaintances are not worse people than those who like a social drink.
Cannabis does affect judgement and coordination to some degree. Cannabis and flying? They don't mix.