Firstly, if two vulnerable groups need protection, leaving both unprotected is not morally superior to correcting this situation with one. Those active in neither animal nor human protection have no basis for criticising the choice of others to participate in animal protection initiative. Rather, if they see injustice in humans not being offered that same protection--they should pursue the provision of that protection rather than try to tear down advances in other areas. Rather than through the puppy back into the fire, they should go in to save the baby.
Secondly, the existance of a protection for animals will in fact encourage the advance of human protection. One famous example of this occurred in 1874 when there was very little legal protections for abused children. So when the case of Mary Ellen, a beaten and neglected 10-year-old girl, was taken by her would be rescuer--Etta Wheeler--to Henry Bergh of the ASPCA because he was known to be a compassionate and influential person. When agencies and individuals responsible for humans would not assist, the existence of a group compassionate towards animals provided a model and a champion for this girl, and this incident was a major stepping stone on the development of the child protection movement.
In summary, equality in suffering is no virtue. It reinforces a status quo where progress and compassion are subject to morally weighted criticism, but apathy and indifference are accepted as the norm. Advances in the treatment of animals should and must be pursued, and if this exposes the vulnerabilities of disadvantaged human groups, then this is better than leaving those situations unexposed.
If we find that we are, in some way, treating dogs better than people, the answer is to treat people better, not to treat dogs worse.
Picture credits: wilhelmien, contracox
See also: Untangling the Animal Abuse Web, I am Only One
For an example of 'people first' see the comment section here.