First of all, this is a clear sign of jealousy. And logic confirms it:
1. Is it really why all foreign students come to study? Because they home countries are inferior?
2. If their quality betters one nation (any nation), shouldn't that nation be better at helping others?
3. How have these shallow accusers been "helping" their own country? Since they know so much about "helping", by paying taxes?
Thus, key elements of jealousy: shallowness, ignorance, doesn't wish the better ones near around them.