First: my son is not a loner. If you see him with his friends he's happy and very involved in the interaction. You can almost see him recharging from the energy of being around people who like him and enjoy the things he likes. He brings his best friend over to our house nearly every day after school so they can spend more time together. At home with the family he's almost never alone in his room. He's out interacting with us, having conversations and looking for hugs. If he has the choice, he'll chose to be around people nearly every single time.
Does he have a lot of friends at school? No. He doesn't. He has three, and two of those are more in passing friendships. They don't spend a lot of time together. His other friends are either home schooled or attend a different school. This has been very hard for him. Because he is a little different (he's weird and proud of it) and he's so small, he's a target for harassing behavior. Kids want to touch his head and tease him. Nothing that would be overtly seen as bullying, but over time it adds up and it tears him down. He hates it. He wants more friends and he wants the kids at school to treat him better.
Second: When you label someone a loner you are saying that you think they are choosing to not have friends. Loners want to be alone, right? But that's not always the case. Actually, a person choosing to never spend time with anyone and not wanting any friends at all is vanishingly rare.
When you say "he's a loner," you're saying: "He wants that. No one is doing anything wrong. I don't have to change what I'm doing. We can all just go about our business and continue ignoring this kid." "Loner" is a way of abdicating any responsibility for the situation.
I see these kids who are alone at school. I see the hurt in their eyes as they walk the halls without friends. I see the way certain children latch on to the teachers, desperate for some positive interaction during the day. I watch them try to interact with their classmates and be rebuffed. Do those kids sound like loners to you? Just because a child doesn't have friends at school, it doesn't mean they are choosing for things to be like that. Most kids want to have friends. We are wired as human beings to be social creatures. When our society blocks a person from that social interaction, it's harmful to them. The pain can be long lasting and affect their relationships long into the future.
Third: When you call my son a loner you call up all the denotations our society has for that word. Loner is what we call the guy who hurts other people. The one who just snaps and makes the evening news with tragedy and pain. You make other people think of those kinds of loners and associate them with my son. Then my son suddenly isn't just a boy who sits alone in class, he's the boy with the potential to cause harm. They might not say it or think it overtly, but you can't live in America and not have that association with the word loner. Calling a child loner can make other people treat them differently, as if that child has the potential to cause harm just because the other kids don't want to be friends with the "loner" child. Kind of messed up, isn't it?
Stop. Stop calling kids loners. How about instead we notice who is alone and find a way to help them be part of the group? Instead of labeling, can we try to heal? Please, for the sake of my son and the sake of all the children who play alone.
They aren't loners. They are people who need friends. Be their friend.