While it is the intelligent to recognize that humans are mostly irrational and can't handle truth, and that you will have better results by working around their defensive instincts - it is still people's responsibility to try to think rationally.
The example of the truck sign is a false equivalence. It would be better if the author said the "Careful, dangerous dog" sign or "electric fence" or "radioactive". If you think of humans as equals, you must also recognize that half of the responsibility of communication lies with the listener. You can become an excellent communicator by taking 90% of responsibility, dancing around people's biases and getting around their defense systems. But that shouldn't be expected of you. If you are right, that should be enough if the listener is doing their part of the communication work. If you insist on irrationally touching an electric fence after being warned about it, that is absolutely not the communicator's fault.
The example of the truck sign is a false equivalence. It would be better if the author said the "Careful, dangerous dog" sign or "electric fence" or "radioactive". If you think of humans as equals, you must also recognize that half of the responsibility of communication lies with the listener. You can become an excellent communicator by taking 90% of responsibility, dancing around people's biases and getting around their defense systems. But that shouldn't be expected of you. If you are right, that should be enough if the listener is doing their part of the communication work. If you insist on irrationally touching an electric fence after being warned about it, that is absolutely not the communicator's fault.