You're right, changing one's worldview is difficult, and we certainly shouldn't force anyone to endorse views they don't hold.
That said, hitching one's identity to unfalsifiable beliefs ("there is nothing science can't understand", "this book is the word of god", etc.) is immature and stunting. It's human nature, but that doesn't make it worthy of respect or celebration. We should strive to get comfortable with the frightening uncertainty in our mental models of the world.
Therefore, insulting religion or irreligion isn't inherently problematic in my book. (Coincidentally, offending people is a terrible way of encouraging them to be more open-minded, but that's a different question.)