CarolC I have to admit I don't know what happens to politicians in the US when they criticise Israel. And though it doesn't really address my point I'd like to hear more particularly about it. I'm guessing they aren't tortured and killed.

When politicians in the US criticize Israel, powerful organizations like American Israel Public Affairs Committee get after them and make it difficult for them to get re-elicted. So although they aren't tortured or killed, there does tend to be a dampening effect on open and free public discourse on the part of US politicians with regard to the subject of Israel.

Foreward published an interesting article about these kinds of political dynamics in 2002:

Leftist Rallying Behind Georgia's Rep. McKinney