(TMZ) - Soulja Boy's fans are turning on him ... blasting the rapper for posting glammed-up pics of the drug codeine on Instagram ... just days after Lil Wayne nearly died from an OD.

Soulja's known for posting pics of the painkiller on social networking sites -- along with giant bags of weed -- but fans went nuclear over these new photos.

Among the angry comments -- "How the f**k u drink s**t that you know can kill you?" and "Who brags about being sad and addicted to prescription medication?"

The comments continued ... "Who the hell thinks drinking cough syrup is cool?!?!? ... Look at lil Wayne had to have his stomach pumped 3x cause that damn cough syrup bulls**t."

Soulja Boy ... where stupid can't get any stupider.