Bashing and mocking Judaism and Christianity is easy and painless in modern society. You’ll get praise and admiration from those within the “right” circles of academia, media, and entertainment. Your opponents will argue with and debate your views and they may even offer (gasp) to pray for you. There’s no real price to pay at all.
However, should you direct the same scathing criticisms towards Islam you’ll find those “right” circles suddenly closed off to you. And your opponents’ rebuttals may not be offered in articles and debate halls, but rather with bullets, bombs, and knives. Standing up to that takes real courage not the false bravado we see on displays as atheists attack Judaism and Christianity.