The Pew Poll is problematic in that it was a phone survey of random phone numbers. Under telemarketing laws they couldn’t call cell phones, which neglected an enormous millennial crowd. Also, many people are reluctant to tell their religion to a stranger who cold-called them, and some people who answer the phone have poor English skills, so I feel like Pew’s figure is grossly underestimating it. CAIR’s finding of 7 million back in 2002 may have been high at the time (they conceded it was probably 6 million but felt pressured to grow the number), but this many years later it still seems plausible to me.
As for boycotts, you’re forgetting that airlines have extremely thin profit margins, about $6 per passenger. You and I aren’t really the customers; the airlines have to answer to investors which are pushing them to increase profits no matter what (which is why even JetBlue let customer service suffer and started putting fees on everything). A $40 million loss would actually be a bigger deal than you think.