Maybe the TV host didn't challenge him because his comments are already so backward and idiotic as to not need further emphasis.
I'll give you a better explanation: the TV host didn't challenge him because it never happened. The "expert" (another journalist, in fact) never suggested to "physically eliminate about 1.5 million of civilians of Donetsk and Luhansk regions that are not able to fit in Ukrainian Nation" or anything close to it.
I'll give you a better explanation: the TV host didn't challenge him because it never happened. The "expert" (another journalist, in fact) never suggested to "physically eliminate about 1.5 million of civilians of Donetsk and Luhansk regions that are not able to fit in Ukrainian Nation" or anything close to it.