Persuading others and accepting their point of view

There's always a time when you're going to have to try and argue with either your friends, family, or anyone for that matter. It is typically hard trying to persuade people to try and accept your point of view on things. There's was this one time with my friends where we were arguing about when I took my wst class and one of the proctors were sitting us all down. I told my friends that there was this one black female who I felt really bad for. The proctor had sat us all down row by row, so we weren't allowed to pick our own seats. When he sat this one particular female down, he told her "If this seat isn't comfortable enough for you, you can sit in the front". I saw the look on the girls face after and felt really hurt. This man didn't say that to anyone else but her. My friends argued that maybe she had told him something before he sat her down entering the classroom but I said no, that is just discriminating on her size or her race. I've experienced one time when eating at a restaurant filled with another race but mine and the waiters were really rude and didn't serve us as well as the other customers. I used experience and testimony as my type of reasoning. My friends later agreed with my point of view on how that man shouldn't have done that to her and that was clearly out of line!