I've said this before, but even if Grimlock didn't know Khanu was trying to investigate INH publicly, he would have still been an accomplice, and subsequently just as responsible, if he had bought Khanu the key and Khanu had gone through with private investigating him. Either way, it's incredibly obvious that Grimlock was fully aware of the fact that Khanu would be returning to the forums to stir some stuff if he had bought him a key, which is why he tried buying him a key. He's done this before.