You might counter that religious beliefs shift more easily than sexual orientation. The prevailing narrative used to be that sexual orientation is totally static. It was useful and effective to frame things this way in the fight for gay rights; it asked, "Why punish someone for something they can't control?" But now that we're at a point in history where every brand under the sun is comfortable running Pride marketing campaigns, what was once an open secret is now more out in the open. LGBT folks have become more comfortable acknowledging that there is indeed fluidity and spectrum when it comes to sexual preferences, orientation, and gender identity. That doesn't mean that a person's orientation can be forcibly changed, but there is an acknowledgement that preferences can sometimes change organically, and we see that with religion as well.
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.)