And that's where your mistake lay.
You do have the right to your own opinion, but the majority of humanity is religious at least to some extent. Of course there are differences in the degree of belief, but the belief is still there.
What's more, most people who are strongly religious feel a deeper connection to their religion than to their race...which is why it's not that unusual to find Black Christians, Chinese Muslims, or White Buddhists.
Now, are you a racist? Do you believe that it's irrational for oppressed races to feel great anger when they are ridiculed for the color of their skin?
The same principle applies to religion, especially given that a great many people feel a deeper connection to their religion than to their race. Ridicule them, and the vast majority will do or say nothing, a few might break your nose...and a vanishingly-small minority - a handful out of the million or so Muslims in France - might decide to kill you....
...but it's that one percent of one percent of one percent that gets the headlines, isn't it?
Again, you've got a right to consider that entire argument BS...but your opinion means precisely squat in the eyes of those being offended at the ridicule.