That's because they are cowards and not necessarily respectful of the latter. They know who not to offend if they want to keep their heads attached to their bodies.
Oh absolutely. There's nothing "respectful" about it, it's simply a matter of self-preservation. They can hit an easy target, appear to be "edgy," and move on without consequence (immediate consequence, that is). That's why I believe, for all the bravado of his animated soapboxes, Seth McFarlane is a pussy.