I think the bottom line is that marijuana is often thought of as harmless, where no drug is harmless to those with addiction problems ~ alcohol, caffene and nicotine included. But to those who are able to be responsible with any of them...live and let live.
Maybe those of us who have lived with and suffered because of a pot addiction get testy because we're sick of pot being called harmless, like it didn't really cause the problems we faced. It's our perception that we're being attacked, probably because the pot addicts in our lives conditioned us to believe there was nothing wrong with their pot smoking. Once bitten, twice shy.
My AH used to get up several times at night to smoke on our deck. Towards the end, he would slam the deck door to wake me up each time, and say loudly (with kids within earshot, thankfully asleep) "Yum Yum, I love the taste of pot. I'll never stop smoking pot. It's my only pleasure."
Sad.