Examples: The way you are acting is offensive! That was offensive. These are phrases are much more harsh than, "You are acting weird." Someone who is acting weird might be stumbling and unbalanced while walking. We might be worried about that person's health. Some teenagers might not like the way one member of the group is teasing another youth. One teen might say,"You are acting weird." This is a way to say the behavior is unacceptable or "Stop doing that." To say someone's actions are stupid is an insult. To say someone's actions are offensive means you think they are behaving very badly. If it were to continue, the police may need to be called to stop this activity. Offensive behavior is not tolerated.

Thanks for the answers.

Being offensive.

You're being offensive is more natural

It sounds unnatural to me. If someone did something offensive, you could remark like "You're being rude." Depending on your relationship with them, you could say "knock it off" as a curt/rude way to tell them to stop being a jackass basically.