For a while I cared for a 10-year-old boy on the autism spectrum. We spent many hours together over many months building a trusting and fun relationship. His mild social skill difficulties forced me to be creative in my interactions and challenged my notions of how to become a better communicator in general.
One day while at his home, he wanted to do something he wasn't allowed to. When I said this, he started to throw a tantrum. He was clearly experienced in how to do this and had likely seen success in getting what he wanted with this method. I knew I was responsible for communicating "no" in a firm but gentle way.
So I threw the tantrum right along with him. I flailed my arms in the same way. I wailed aloud. I threw myself on the floor with the same dramatic motion. This shocked him. Clearly an adult had never responded this way before. Over time he relaxed, and we avoided the prohibited activity.
My tantrum was effective because I changed myself to meet him where he was at in the moment. A message must be framed with the recipient in mind or it won't be heard.