I know that for me personally pot is harmful. If it wasn't I would use it regularly, but it is massively demotivating for me, a side effect I think that gets minimized more than it should. Besides that it causes anxiety for me, paranoia, etc. Then there's the stupidification factor, which coupled with the anxiety and paranoia can absolutely disrupt my normal behavior in favor of avoiding contact with other people.
It's not like that for everyone. Not sure why the effects are so different from one person to the next but I know many people who claim none of the side effects I experience. Many claim the opposite, that it calms them down and makes their thinking more clear and gives them a desire to go out and have a good time. If I used pot going out in public would be the very last thing I would want to do. It'd be munchies and goofy comedy shows time for me.