'Odd Future' Concert Victim -- I'm Getting Violent Threats from Blood-Thirsty Fans!

A fan who suffered a nasty onstage beatdown at the hands of rap group Odd Future continues to be viciously attacked ... only now, it's by bitter fans on the Internet -- and the 17-year-old tells us, he's scared for his life.

TMZ broke the story ... Chassan Rasagi got his ass whooped by the group after jumping on stage at an OF show in San Antonio earlier this month -- and claims he suffered serious injuries as a result ... including lacerations, scratches and burns all over his body.

Rasagi filed a police report immediately after the incident -- and has since lawyered up to sue the group -- but now, he tells us he can't even go online without facing relentless torment, anti-Semitism, and violent threats from OF fans. Among the threats:

-"Needs to get his prepubescent face smashed again..."
-"Is a f**king #f***got ass bitch made honky #OFWGKTA should of shoved a mic up your white ass"
- "Learn to take a beating you f**king Jew ass"
- "You a straight P***y dude"

The cyber terrorism's gotten so frightening ... Rasagi says he's started to keep track of the messages ... because he fears he might get jumped, or worse.

We reached out to Odd Future -- so far, no word back.