I've been told that repeatedly by pot advocates. And have seen it all over the internet. Smoking it alone is bad for your lungs but have been told no it isn't. Cigarettes of course are bad but inhaling pot smoke is no big deal to hear some tell it.
I can only speak for me and I have never heard anyone or read anywhere that 'smoking' anything is not good for you.
I have not smoked weed in over 9 months nor anything else for that matter.
I either vape at 384°friend or less or via edible form.
Cannabis causes memory loss with regular usage but it has not proven to be permanent yet but I would assume it does.
Cannabis, like any drug, can have unintended side effects based on the individual.
It can cause depression when usage in medicinal doses for an extended period of time.
All that said, cannabis is probable safer than aspirin or any of the NADs or certainly NASs.