It's our mission as science communicators to, well, communicate science. And not just its processes and methods, but also the value and importance of science in modern society. But there's a dangerous line that's very easy to cross when promoting all things science: that science is all the things.
Let's look first at the difference between patriotism and jingoism. It's perfectly fine and acceptable to be patriotic: to love one's nation, its people, its ideals, and to strive to make it better. It's another to turn that love for one's own country into a hatred for others, to believe in its superiority over all the other nations of the Earth, and to use that belief to back aggressive aims.
Scientism is the position that science isn't just a cool way to learn things about the universe, but The One True Way, superior to all other paths of knowledge and understanding. Something along the lines of "If it ain't science, it ain't nothing." That science is capable of answering any possible question (or at the very least, arguing that the only questions worth considering are those that are amenable to the scientific method), and that humanity can safely discard religion, philosophy, and even the arts as relics of the past.
I'm not saying that it's our job to promote anything but science - we are to be clear, strong-voiced advocates for its value. But the people we are speaking to are real humans with real lives with real beliefs. The moment we switch from promoting to attacking, we stop communicating, and we've failed our mission.