People are funny. We delude ourselves into thinking that if we don't actually verbalize our rejection of someone and tell them in spoken words that we have rejected them, they won't know they are being rejected.
We don't realize how often our actions send a message just as easy to understand as any verbalization of our feelings.
Ask anyone who has been rejected by a person or group of people. They will be able to explain the subtleties, or not such subtleties, of body language and attitude that led them to draw the usually correct conclusion that they themselves have been found wanting in a particular social situation or in a specific group.
When we are obviously excluded from a group project, when people all around us are talking to each other but never directly addressing us, when someone we are talking to appears uncomfortable, doesn't want to look us in the eye and makes a rather quick escape based on the flimsiest of excuses, it isn't that difficult to conclude we are not welcome, not accepted.
So let's not fool ourselves into thinking that just because we deem someone else as being unworthy of our wonderful selves that they are also too stupid to understand what we are telling them by our actions and attitudes, even when we try to be subtle in our conversation.
Remember what condition we ourselves are considered to be in by our Lord and how he has redeemed us and made us worthy of his glorious Kingdom. If we realize we are forgiven from our own sorry state, how can we hold ourselves above another human being in no more sorry state than we ourselves have been?