Misunderstandings about animal rights: cruelty to impure animals.
Islam is a religion that is devoted to the concept of grace. Muslims are asked to be gracious to one another, to all people, to animals and even to the environment. God is Most Gracious and all grace comes from Him. When the Prophet Muhammad described the grace of God, he used to choose the metaphor of an animal mother who is gracious to her descendants. 
„And We only sent you out of mercy for all worlds.“ (Quran 21: 107)
Islam is also concerned with protecting and safeguarding rights. The Shariah, or the laws of God, as embodied in the Quran and in the authentic traditions of the Prophet Muhammad, strive to protect the rights. Human beings have both rights and duties. One of these obligations is to protect animals‘ rights to security, security and friendly treatment. We are responsible before God to ensure that animal rights are upheld and respected. Cruelty to animals is a serious sin and can result in harsh punishment.
„A woman was tortured and thrown to hell because of a cat that had locked her up until she died of hunger.“ The Prophet Muhammad, God’s blessing and peace be upon him, said: „She did not give her food or water when she was locked up, nor did she release her so that she could feed on the insects of the earth.“
It is true that God made certain animals unclean, especially the dog and the pig. However, this is not a license for cruelty. Impurity simply indicates that certain precautions and special rules must be followed when handling these animals. Treating animals, including dogs, nicely can result in a big reward; just like the cruel treatment of animals can bring a person to hellfire.
The Prophet, God’s blessings and peace be upon him, said: “When a man went he felt thirsty and he went down into a well and drank away. When he got out he saw a dog panting and eating the sand with thirst. The man said: ‚This (dog) has the same problem as me. Then he went down into the well again, filled his shoe with water, held it with his teeth, climbed up, and gave the dog the water. God thanked him for this (good) deed and forgave him his sins. ” People asked, „O Messenger of God, will there be a reward for us if we give to animals?“ He replied: „Yes, there is a reward for every living being.“ 
God has made it abundantly clear that pork meat is impure  and that the dog is an impure animal. Undoubtedly there is divine wisdom behind all of this; however, a Muslim willingly surrenders to God’s orders without knowing the reason behind the divine instruction. In addition, God specifically said that a believer hears and obeys His Lord’s words.
„‚We hear and we obey.“ And it is they who will succeed (and who will come to paradise forever). “ (Quran 24:51)
Hearing and obeying the laws that God has sent down cannot be interpreted as a license to be cruel to any living being. Although pigs and dogs can obviously harm human beings, such as how many diseases and bacteria can be transmitted through pork, or packs of dogs can cause disease, there is no justification for being cruel to them.
The Prophet Muhammad ordered the elimination of the dogs from Medina  and the reason for this was that the dogs were infected with rabies at that time. Rabies, as is well known, is an acute and deadly infectious disease that causes seizures in humans and ultimately leads to death. There were no animal shelters and no vaccinations for sick dogs; therefore killing dogs was the only feasible way to protect people from harm.
“My father (one of the companions of Prophet Muhammad) said:“ During the lifetime of the Messenger of God, dogs used to urinate and walk (come and go …) through the mosques ”
Islam is clear about animal rights, they should be treated with grace and kindness; however, it is important to remember that the animals were created for the benefit of mankind. We are not allowed to abuse them or strain them beyond their capabilities. On the other hand, it cannot be accepted to consider the life of an animal at the same level or higher than the life of humans. It is therefore permitted to slaughter certain animals for eating or out of necessity; it is also allowed to use animals to advance medical science. In both cases, cruelty is prohibited.
Humanity is allowed to use animals to meet their legitimate needs, but not their lower desires. Any experimentation for luxury purposes is prohibited. A believer must be certain that the meat that he is has been slaughtered in a human way.
Umar ibn Al Khattab, the second Muslim leader after the death of Prophet Muhammad, saw a person pulling a goat by her leg to slaughter her. He said to him, „May ruin catch up with you, slaughter them appropriately.“  Umar told people that animals should not be treated harshly or unkindly. He expressed his concern for animals and his fear that God would ask him about his treatment of animals by saying: „If a camel stumbles in the Euphrates valleys, I fear that God will ask me about it.“ 
Humanity has been appointed as the steward of God’s creation on this earth. Treating animals with kindness and grace is just one of the duties that are embedded in this administration. The impure status of some animals does not affect their right to live free from pain and suffering.
 Sahieh Muslim
 Sahieh Al-Bukhari
 For more information see Why pork is prohibited, parts 1 & 2 (http://www.islamreligion.com/articles/2513/viewall/)
[4 ] Sahieh Muslim
 Sahieh Al-Bukhari
 Dr. Mustafa Al-Sabai. Some Glittering Aspects of Islamic Civilization, Sharif Ahmad Khan, trans. (Delhi: Hindustan Publication, 1983) p. 138
 Sheik Muhammed Karakkunnu, Farooq Umar (Malayalam), Calicut, India: IPH, 1984) S. 516.