McCain was elected in 1981 and Keating began sending money contributions in 1982. McCain was obviously "green" enough, naive enough, not to figure it out. Something which may account for his ill concieven Campaigh Finance Law.
What McCain did wrong was not to report and pay for the aircraft trips in Keating's plane until late, that's it. If every politician who did that were to leave office tomorrow, you could count the remaining members in each house on one hand.
Being anoyed at McCain is perfectly reasonable. Feankly, I'd rather we had Duncan Hunter for a candidate. But we must play the hand we are delt, no matter how much we wish there was another.