Sure, what sort of "proof" do you require? How many talks from the leading mormon authorities would you like to read on the subject? Will a statement from a practicing mormon suffice?
First, mormonism teaches a different view of the trinity from main stream christian churchs- which get their view from the 3rd century nicean creed. On that basis alone, mormons are considered non-christian; dispite that fact that they view the only road to salvation is through Jesus Christ, the Son of God. They don't judge other views of the trinity as defining a person as christian or non-christian.
A more pragmatic appoarch, judgement by ones behavior. "By thier fruits ye shall know them".
And Second, you obvious lack understanding of mormonism's doctrine of the afterlife, which doesn't include a "hell" except for the select few who out-rightly betray the Savior after recieving a witness of him.
So on that- no, mormons do not think that the rest of christianity is going to burn.
And try to be more polite when posting - it makes you come across better
got any quotes from Young or Smith saying other Christians were true believers?