I think rap prior to 'gangster rap' (the likes of the aforementioned NWA plus the artists like Ice T and Ice Cube, etc) was certainly less 'gun yo down nigga'. From there, imho, it did get a little bit silly.
Prior to that scene, rap seemed to me to be funk inspired word trickery. I'm thinking Grand Master Flash. And often seemed to be inward looking; raps about raps - 'my rhymes are best'. Public Enemy changed the game and were, imho, brilliant. Intelligent and eloquent. They were uppity! As delzegg mentioned, they scared people! Then along came NWA. I liked them hugely but they turned it up to 12 and positively thrived on creating outrage and fear. And the solo Ice Cube did more so when NWA split. (Ironically, Dr Dre is almost establishment these days! A very respected record producer and exec). Then, as I said, it seemed to get silly and I pretty much lost interest in rap.
That said, I rate LL Cool J. He was one rapper that, for me, managed to span the silly era without getting caught up in it.
Rap has calmed down though. I mentioned Dr Dre, and he's one of those that has focused on producing rap as music rather than posture or, worse still, a form of gang warfare.
And rap has produced, again imho, two of the most chilling albums of any genre. Ice T's 'OG: Original Gangster' and Emminem's 'The Marshall Mathers LP' (Dr Dre produced btw). The latter will probably surprise no-one but the former... well, for me it's a superb evocation and, to some extent, critique of the era. Ice T's a clever bloke, he wasn't 'big upping' it, he was telling it as it was.