Because they all fit together somehow...
Along with hating women, music, art, kites and countless other innocuous things, Islam also hates dogs. It doesn’t matter that dogs are loyal creatures who love unconditionally and are part of God’s creation…if Mohammad hated them, then Islam hates them. (Via.)
Keeping dogs as pets, according to the Tehran Times, has become remarkably common among Iranians, particularly those living in metropolitan areas. Police have been assigned the task of confiscating dogs from people who walk them in public. The confiscated dogs are destroyed and burned in incinerators.
The istifta inquired why is a dog considered unclean under shariah despite a lack of any references to dogs in the Holy Quran.
In his response to the istifta, Ayatollah Makarem Shirazi emphasized that under shariah, dogs are, indeed, filthy creatures that no believing Muslim should touch, let alone keep as a pet.