If you want to play or specific game modes without bots, you can use the developer console. This requires a tiny edit to your game files.
This is the most annoying part of playing offline. The game aggressively wants to phone home. Simply wait 10 seconds or click "Cancel." The local menu will load. If it doesn't, go offline on Steam (Steam > Go Offline), then launch the game. how to play call of duty black ops 1 multiplayer offline pc
Scrolling past lines about mouse sensitivity and shadow quality, he found it: If you want to play or specific game