"First of all, have we used the G word?"
Yes the Bush administration used the word "Genocide" to describe what is going on in the Darfur region. Colin Powell was the first to say as such in the Bush admin.
http://72.14.203.104/search?q=cache:ls71BifXC2MJ:news.bbc.co.uk/2/hi/africa/3641820.stm+darfur+genocide+colin+powell&hl=en&gl=us&ct=clnk&cd=1
"we didn't venture into Iraq because he was committing mass murder of his own people but because he was sponsoring & underwriting terrorism."
But these Rebel groups aren't considered terrorists?
Is that what you are trying to say? Or is it the fact that they haven't targeted American interests?
"If the UN determined that what is happening in the Sudan is genocide then they are required to act."
The UN refuses to categorize the acts taking place in Darfur as Genocide, but the US government has in fact acknowledged this.