If you have underlying issues with anxiety and paranoia, adding marijuana to the mix exacerbates these issues greatly and becomes a poor crutch for dealing with them. I've seen friends and family who smoked 2-3x weekly for a few years develop eyebrow-raising mental problems. So I tend to agree.

Personal anecdote, N=4.

(Yeah of course, alcohol is just as bad, or worse in extreme cases, but people can usually sense the damage being done to them by it afterwards. Pot's effects are internal. It's hard to reflect until it's too late.)