Listen, I have nothing in particular against DXM or any other way of getting high, for that matter. But some might say that at least crack is a legitimate drug. I'd say the general consensus on chugging cough syrup is that it ranks about on the same level as sniffing glue or computer duster or whatever other household products can be abused.
Again, my point isn't that crack is good or that DXM is bad - just that who fuckin' cares? I've smoked crack, you've smoked crack. Neither of us habitually smokes crack, ergo neither of us is a "crackhead". Feeling ashamed is pointless.