Are prohibitionists really this stupid?

[Rollo]

did the study make the distinction between those who smoke marijuana mixed with tobacco and those who smoke it straight?

They made an effort to make the distinction.
Smoking both marijuana and tobacco was common among marijuana users (77%). This prevalence was higher than that noted in other studies of marijuana and tobacco use, which may be due to different definitions of marijuana and tobacco use across studies.

should tobacco become a class b drug then?

You tell me. Show workings.