It is not cowardly, as has been pointed out, he is doing this in public.
It is not illegal, either: you can destroy anything that belongs to you. It might violate laws against open fires, such as those against burning trash inside the city limits.
If burning the national flag is protected free speech, burning a Koran is clearly protected free speech as well.
It is simply a stupid provocation by a stupid and hateful man. None of his church's 50 members seem to agree with it.
The idea that one ideology can triumph over another through silly ritual acts like this one is a fallacious one.
I think someone sent Bibles in Pashtun and maybe some other languages to some soldiers in Afghanistan to be given to the locals, and the US military confiscated and destroyed them, but that was not done publicly and was done to prevent the Afghans getting pissed off at the US military.
The only purpose of this fool doing this is to annoy Muslims. I do not see how he can be arrested or prosecuted, though.