Evacuee implies an orderly and organised process. Refugee implies a desperate, involuntary and unplanned move. The former doesn’t have the emotive implications or emotional force of the latter. Whatever its dictionary sense, or the definitions of the international aid organisations, or the plaints of politicians, or the lexical views of dictionaries and pedants, for most people refugee sums up the situation of the sufferers more accurately than any other.
As I said previously, it's too bad when sensitivities effectively ban a neutral and descriptive word. The English language as a whole suffers for it.