I didn't know MS-13 has rules about attacking civilians. There's obviously maniacs who dont give a fuck...but the "higher ups" prefer to keep their shit between rival gangsters. Says it keeps them out of the polices way. They don't even like it when their members are drinking in bars because the chance of getting in brawls with regular people goes up.
Read all that in the story about the dude who went undecover in MS-13 and busted a bunch of them
http://www.newsweek.com/2018/06/22/ms-13-972406.html
Crazy story if anyone wants to read it