Other religions get poked at all the time. They get used and misinterpreted by media all the time. It happens constantly. How quickly we forget the Charlie Hebdo thing. And if you belong to a smaller faith, like a pagan or whatever the people call themselves who worship the Norse pantheon these days, it's infinitely worse. Christians aren't some uniquely poor, set-upon demographic here, they're not treated any differently than anyone else (better than some), they just tend to complain about it more than most (not all, but most) when it happens. The only group that readily comes to mind that complain even more are Muslims when their Muhammad is featured, and apparently that is a huge cardinal sin for them, so I can see why they'd get uppity about that.
DC has every right to publish what they like, but it's a shame to see a company give in to ethical terrorism like that. Certainly this book wasn't going to generate enough revenue to make the complaining worthwhile, but anyone could see that going in, and if they were that worried about it.....why green light the thing in the first place? It's sloppy management.