Can marijuana be used responsibly just like alcohol?

I’ve noticed this stigma, even on this site, where many people assume that you can use alcohol in a responsible manner, but not cannabis. Considering that alcohol destroys many lives despite the fact there are those who use this drug responsibly, and these points that NORML brings up, this makes me ask the following question below.

Why do people assume that alcohol can be used responsibly, and that you can be a respectful person while doing this, but not with cannabis? Is this stigma associated with cannabis use based on merely stereotyping the users of each of these two drugs, or is it something more? Moreover, are these stereotypes justifiable in your opinion?

Note: I have asked this question in the general section because I don’t want the comments on such a potentially vague topic to stray away from what I’m trying to ask in the latter paragraph. (I better state this again) I want to know why there’s a stigma associated with one drug, but not the other concerning responsible use and the respectability of a person, and whether this is justified or not in your opinion.