I concur with the purple banana.

The fact that you are asking the question "Is it OK to be high at a family event" is just the Reagan era propoganda melting your brain. That tells me your family obviously wouldn't approve, but it's not really a question of morality, rather general judgment.

Is it moral to stay out past your curfew? Is it moral to binge and then purge, or just starve yourself? These (including smoking - weed or cigarettes) are amoral. They may have a detrimental affect on your health to some degree, which makes them a health issue, not one of morals.

Morality might rear its ugly head when your five year old niece, who you already know before hand needs lots of attention, gets ignored by you at the movie she's all excited about and shouldn't be watching because you're to stoned (ie - selfish) and let me tell you, she'll remember it. The devil is in the details.

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a clean bong is a sign of a sound mind