Noted challenging the spot of the ball with an 18 point lead in the 4th is going for the kill. If I am not mistaken when that drive did stall they went over the top immediately for a TD. I have no problem with going for the kill as you say but a challenge like that is a glorious waste of time and he and Andy Reed are the worst at it.
So what does being up 18 have to do with whether you challenge or not? You challenge if you think it will help your team win. Not saying it was a good challenge in the case. Just saying he's doing what he thinks will help the team win.