No one would blame a Muslim for being offended at a "Zombie Muhammad" costume, just as no one would blame a Catholic for being offended at a "Zombie Pope" costume. But we do object to people becoming physically violent over their disagreements. In this case, a Muslim attempted to choke an atheist who was mocking Muhammad. Why would the Muslim get violent? Because Islam promotes violence towards people who mock Islam.
No real surprise there given many Muslims consider any physical depiction of any kind offensive. Yes, the costume was in poor taste and offensive, but in this country you have the right to say almost anything you want, even if it is stupid The man should not have been choked for just wearing a costume that shows how ignorant he is. Letting him wear it would have been punishment enough.
Answering Muslims: Muslim Attacks Atheist in Pennsylvania over "Zombie Muhammad" Costume