请不要称外国人为老外，尤其是别当面这样叫。这个词让人感到像个局外人，甚至是不受欢迎的，意味着隔离和不可逾越的差异，扩大当时已经存在的差距。
Please refrain from calling a foreigner a foreigner especially in his face. The word makes people feel like an outsider, and even unwelcome, suggesting separation and insurmountable differences, widening an already existing gap in the situation.
(Source: wwenglish.com)