This article contains profanity, sarcasm, and dramatic hyperbole.
The basic point of it is that when children do mean things to each other, adults often tell the children, "It is just because s/he likes you." (The article deals with boys picking on girls, but the author admits in the comments that girls do it to boys, too. Personally, girls will pick on girls, and boys will pick on boys, too.) When one stops and thinks about it, this message is incomplete. In some cases, one child is picking on the other because that child cannot properly express his or her feelings on interest in the other child. However, sometimes, one child is picking on the other because that child is having a bad day or because that child is not very good at empathy yet or any number of reasons that have nothing to do with the one child liking the other child.
(As a personal anecdote, I was bullied as a child. I was, in fact, once carried off to the playground because I couldn't walk, sent to the emergency room, had to get x-rays, and had to have months of follow-up treatment as a result. I do not recall that the boy was punished in any way. Did the boy do this to me because he liked me? He certainly did not. He did that to me because I had something that he wanted and he thought that yanking a heavy object out of someone's hands is an appropriate method of acquiring the object. In other words, he was not yet mature enough to know that stealing was wrong, and that lack of understanding was why I had to go to the hospital. Liking had nothing to do with it.)
So, teaching children that, "It is just because s/he likes you," is an incomplete message, and it fails children in some ways, because there is a valuable teachable moment to be had there. Instead, adults could say something to the effect of, "No one should ever insult you, touch you in a way that makes you feel uncomfortable, steal your possessions, or hurt you. If someone does this to you, you need to tell him or her in a loud, firm voice, 'No! Stop doing [whatever the offensive action is]. I don't like it.'" Then the adult and child can practice saying this out loud, because from personal experience, it takes some practice to become comfortable shouting in a clear and assertive manner. Then the adult can further explain, "Some adults will tell you that the other child is doing this offensive action because he or she likes you, and then that adult will laugh it off and do nothing. This reaction is not appropriate of that adult. If the action is upsetting you, then the matter is important to you, and the action needs to stop. Now, there are many reasons why another child might do this sort of thing. He or she might be having a bad day and is taking it out on other people. He or she might not have a lot of self-confidence and might feel that hurting other people makes him or her look cool. He or she might not yet understand that other people have feelings, too. Sometimes, he or she might be doing it to express an interest and is expressing that interest in the wrong way. However, whatever the reason why this child is doing the offensive behaviour, it is inappropriate, and it needs to stop. If the child is really doing this offensive behaviour to express a friendly interest, he or she is just going to scare away potential friends, because no one wants to be treated like that and that is not how anyone should treat their friends. So that other child needs to learn better ways to express his or her interest, which will be better for everyone. Never let anyone treat you improperly, whatever the reason."
Think about it for a moment. Even if a child is just acting out because he or she has a friendly interest in another child, what good does it do to let that maladaptive behaviour continue? It does not do any good at all. The sooner that child learns appropriate ways to express his or her feelings, the better.
On the other hand, if the child is acting out for some other reason, addressing the root cause of that maladaptive behaviour is still a good idea. Maybe the child does not know to properly deal with his or her anger. Maybe the child is hungry, because there is not enough food at home, and that makes the child cranky and violent at school. There could be any number of reasons.
Finally, I think it is a good message to teach children that they should not put up with annoying or worse behaviour from other children and especially they should be taught that is not how friends should treat each other.