It depends on what the person gets out of it.
For most people, smoking pot is just a fun way to relax. But if some people get something more out of it; if, for example, someone gains new insights into a movie or piece of music while high that he/she hadn't gotten before, then it's not really anyone's place to bash that person for it.
I doubt I'd be a fan of some of the musicians that I'm a fan of now (I know, I know, lolz, Muse, right? But I actually like a pretty wide range of artists across many genres) if I hadn't listened to them while smoking pot. When I first started smoking, it really helped me cue into subtle things in the music that I would normally overlook. Now, I tend to hear those things whether I'm sober or not, but back when I was 18 or 19 it helped a lot. I don't feel like it's anyone's place to attack someone for expressing a view like that.