He only mentioned not having a warning because of everyone saying he's had millions of them - I don't believe he's using that as an excuse, just making that point.
He's a smart guy and obviously knows that forgetting about the draft time was a bad thing. All that mistake would do was to hurt the team he's working so hard to build... why should we punish the team even more by forcing a change? And (more selfishly) why should other members in the league have to suffer the consequences of this decision?
He clearly cares about this GM job or he would have resigned last night instead of taking all this flack.. or just not bothered replying.
Ultimately any of his mistakes (like the mistakes of any other GM) only damage the team and have no real impact on anyone else. I just don't understand, if all the Seattle teammates are happy with the direction of the organization, why a change is even being considered at this point in time.