"Brooklyn Nine-Nine" star Terry Crews tells TMZ Sports ... back when he used to play for the L.A. Rams, the Raiders fans hated his team so much, they THREATENED his wife and family. 

Crews -- a former NFL linebacker -- played for the Rams back in 1991 ... back before the Raiders ditched L.A. and moved back to Oakland. 

And last night in L.A., Crews told us some of the more insane fans of the Silver and Black took the rivalry so seriously, they threatened his wife and family. 

It's pretty crazy stuff -- but Terry tells us it's not the Raiders fans that people need to worry about these days ... there's ANOTHER team in the Bay Area that's even scarier. 

Check out the clip.