Otha:
leaving aside the fact that I don't GM Amber, and have only played it in extremely bastardized ways (IE: not IN Amber, just using the rules) and that was some time ago...
If a player reacts viscerally to a color situation is if it were of great personal concern, I rather suspect a time out is called for. I don't play to push peoples buttons. If he's that hot under the collar that he's dictating the game, player to GM, then it will be disruptive not to take a quick break.
If the problem is one where he can't get past the fact that we are talking about imaginary children in an imaginary orphanage, it tells me there is a serious issue at hand. Its one of those things where I need to know if its going to pop up fairly often. If it's a one time thing, taking a break and picking up a few 'hours' down the line where the orphanage is more a memory might be the best solution, if on the other hand the player has a wide 'issue zone' where anything remotely like this will set him off, he needs therapy, not my game, and I'm not going to see my game turned on it's ear. Like I said, my evil people are evil, nasty and bad... a nicer fluffier GM is going to be more this guys speed.
If I DON"T stop the game at that point, then I'm going to keep burning children and butting heads with this guy, and either way the rest of the night is probably going to devolve into a showdown between him and me... not a good way to go out.
Of course, i could be reading into your example.