The line between harmless fun and bullying is not difficult to determine. Bullying is never harmless. And the only way fun is harmless is when it is fun to all involved. Remember the foundation for our culture and constitution is that we have rights and can exercise those rights freely up to the point that we impede the ability of another person to do the same. Bullying is an attack, plan and simple. It may not always be physical but it is an attack just the same. Anyone who resorts to bullying needs to take an introspective look in the mirror. Aggressively attacking or forcing your will on another person is a compensation mechanism. Your actions are caused by your own faults. This also means that bullies are less of a human being than the ones they bully.
There is no line between bullying and harmless fun. They are the antithesis of each other. Bullying is unfair, condescending, and detrimental. You may feel like you are building yourself up but if in doing so you have to tear down someone else it’s wrong. And it is that simple. Bullying causes mental anguish and emotional pain; so how can this be harmless. And in no way is it a right of passage. It is in no way a right. And if one feels like forcing thier will on another or threatening or harming another person is fun then there is something very wrong that person.
Actions that are considered bullying are never harmless and should never be considered fun. If you are in a group where picking on someone is tolerated, or even expected, and it is even on all fronts, then and only then is it permissible. But that is also not bullying. And it may be fun, but if it is not fun for everyone involved then it changes faces and meaning. So it is not a matter of crossing a line, it is more akin to completely changing direction. Those who bully seek control and think fulfillment only comes at the expense of others. But bullies should remember two very important things before they choose that path. First is seeking control in this manner will lead to loss of control. Intimidation and force will only carry one so far and when those tactics are employed or necessary then it usaully means that the desired outcome is in and of itself the wrong outcome. Otherwise it could be obtained in a more passive and mutually beneficial way. Second things is everthing has a breaking point. Once you reach that breaking point there is no alternative and no way back and you will have to accept and live with whatever happens.