using the word 'head' as a suffix in this manner indicates the desparity and unnecessary dependence a person has on the substance that the preceding word describes. there's cokehead and smackhead (i guess) . You'll notice there's not a lot of other labels people use for those hooked on coke or heroin. However, for those exclusively of the marijuanian persuasion, there are several appellations that I don't need to list that people use with a certain levity, having a degree of a sense of humor about it. Anyway, I think 'pothead' is definitely used as a contemptuous label to classify us into a category same as those actually hooked on harder drugs, as one who instead of having a brain in his head, it is actually filled with pot because it's all he's capable of thinking about. I'm personally offended by very little, but I know the spirit that's intended when I'm referred to as a 'pothead.'

PS didn't the guys in half baked get stamped with the word 'pothead' one by one like it was a label?