I honestly don’t know if idiots being islamaphobic helps or doesn’t help with terrorism. The reason ISIS (and islamic terrorism in general) is appealing is because the narrative is that you get into paradise if you murder infidels and die in the process. More Americans were Soviet Unionaphobic throughout the Cold War than were Islamaphobic in 2001, and there weren’t concerted efforts by seemingly ordinary Russians or communists to murder innocent people.

Also, maybe it isn’t an outright justification, but I think that it’s clearly a tacit one at least. It places blame on someone who isn’t the terrorist. Sam Harris has said before that the fact that deposing a dictator like Saddam Hussein (one of the most evil men of all time) makes a country worse says nothing bad about us, but it says something terrible about the state of the Middle East.

EDIT: To be clear I’m not saying that it’s a justification of the terrorism itself, but of why it happens.