Trump Supporter Charged With Assault for Spitting on BLM Protester

The Trump supporter who spit on a Black Lives Matter protester on camera during an argument has a big problem ... he's now a criminal defendant.

Prosecutors in Massachusetts charged Scott Marberblatt with assault and battery. An officer on duty at last month's protest said he witnessed Marberblatt spitting and coughing on a BLM protester.

The alleged victim, Marcus Johnson, tells TMZ ... he was with his mom, who was holding a BLM sign, when the guy started arguing with them that "all lives matter" ... then suddenly, he was on the receiving end of the gross discharge.

Aside from the obvious, Marcus had a deeper concern -- coronavirus. He says he couldn't get a COVID test immediately after the incident, so he self-isolated for days. He says he was finally able to get a COVID test, which came back negative.