Who says they're not? Burning the holy book of any religion is stupid and hateful, especially when your intention is to demonstrate how much you hate that religion and anybody who believes in it.
Islam and Muslims don't deserve any special treatment, but does anyone REALLY believe that Islam in this country is treated even remotely the same as Christianity or any other religion in this country? Lest we forget, this "Koran burning" event was preceded with several months of "Ground Zero Mosque" debate, with many high profile pundits and politicians basically equating a guy building a community center with terrorist scumbags.