"Or, alternatively, you could get a grip."
Or you could be mature enough to know this sort of things just inflames and starts fights.
It is the equivalent of yelling fire in a theater. Why intentionally provoke a group of people? I think Islam is nonsense, but I would NEVER deface one of their religious symbols to make a point - it wouldn't change one Muslims mind and it could start an unnecessary altercation. Besides, the Darwin fish sends a message that Darwin is your deity. I thought that wasn't so with the "pure" scientist? Professor, you know that such things are bad form, just as a Christian getting in your face and trying to provoke is.
Because debate often employs satire and even ridicule. As a former Christian, I don't find the Darwin fish offensive, and I didn't even when I was a Catholic. It's rather gentle humor, and not at all bad form. Describing kids in public school as the descendants of rats and cockroaches, now, that's bad form.
Nor do I believe religious symbols deserve any special protection that other symbols do not deserve.
If I'd seen you object to the frequent posting here of the old lithograph with Darwin on a monkey body, I'd grant that you're at least consistently humorless.