A. No, logically that is not true. Saying something is beautiful does not mean something else is ugly. Similarly, just because something is ugly doesn't mean that something beautiful exists.
To illustrate: if there are 5 paintings, and these are the only paintings in the world. I describe one as beautiful. That does not imply that the others are ugly. The only thing that it implies is that the painting I just described is beautiful, and mentions nothing of the others. Even if I said the painting was the
most beautiful it doesn't imply that any of the others are ugly. In fact, it's possible that
all of the paintings are beautiful.
B. Again, no one is harmed. Since I have just proved that beauty does not imply ugly. It's possible for all to be beautiful even if some are more beautiful than others. But even if there were ugly people none of them is harmed because you are not actually calling them ugly. You are not specifically identifying anyone.
C. Huh, by quoting the dictionary you just proved my point. When you call someone exotic you are calling them a foreigner which is ultimately calling them an alien. So think on that.
Look, I'm tired, and I feel like I'm going on in circles, so I'm going to tell you straight up. Maybe you don't think there's anything wrong with implying that someone is a foreigner. But this is hurtful to a lot of people, especially if they live with the "
perpetual foreigner" stereotype. And when you call someone "exotic" you reinforce that stereotype. Regardless of your intentions this is a demeaning thing to do.
Step outside of your own shoes and see why people object to this and why they wouldn't want to be referred to in this way. It's pretty simple.