1947 Invasion of Kashmir, which was conducted by Pakistani-backed tribal invaders is how the blame lies at Pakistan's door. States were given a date (which, if my memory serves right now, was somewhere in the middle of August), to choose whether they wished to secede to India or Pakistan, Kashmir chose neither and as that time-frame ended, it was de-facto independent.
I do accept the fact that Kashmiris on the Indian Side are treated more like cattle than people, and it's why I care for the well-being of the Pakistani state, but all aside, you cannot justify Pakistan's claim to Kashmir on the basis of atrocities and human rights violations. Political suppression still occurs in AJK/GB, and that is a fact.
Erm you do realize right that the tribals did not enter Kashmir before October right? By this time widespread massacres of Muslims had been committed by the Maharajah? Whilst I am in a hurry right now I will return later to show how the Maharajah had already decided that he would join India whilst keeping up a facade of an independent Kashmir(Prem Nath Bazaz reported this). For now the below links should help.
"There is evidence that from the outset regular troops and police in the State service joined informally and covertly, but enthusiastically, in these atrocities which, some have estimated, eventually resulted in the death of atleast 200,000 Muslims and drove twice as many into exile.
By the beginning of October the Jammu & Kashmir State authorities joined openly in this anti-Muslim policy by setting out to create along the State's border with Pakistan (in the region of Gujarat and Sialkot) a depopulated zone some three miles deep. Hindus here were evacuated. Muslims were either killed or driven across into Pakistan. On a number of occasions Jammu & Kashmir State Forces actually crossed over into Pakistan and destroyed villages there(well documented acts of Jammu & Kashmir State's "aggression" on its territory which Pakistan has signally failed to exploit in its arguments concerning the rights and wrongs of the Kashmir situation). Early in October British observers saw in one such village on the Pakistan side of the border no fewer than 1,700 corpses of slaughtered Muslim men, women and children. Before 22 October, a crucial date on the Kashmir story, the Pakistan authorities reported that at least 100,000 Muslim refugees from Jammu were being cared for in the neighbourhood of Sialkot. The Government in Karachi might talk about negotiations, but there was a growing body of opinion in Pakistan, particularly in the Punjab, which argued forcefully for more direct action to stop the killing."
Alastair Lamb, Incomplete Partition, Roxford 1997, p.128
Restlessness was universal. In Punch, where thousands of demobilized Muslim veterans live, an open armed rebellion broke out against the Maharaja and his administration. The rebellion spread rapidly to the adjoining area of Mirpur, where was veterans also lived in large numbers. Instead of realizing what he had done, the Maharaja egged on by Congress leaders and his new counsellors, dispatched the whole of the Dogra Army to quell the disturbances, or as one colonel put it, to reconquer the area. The army perpetrated unheard of atrocities on the people of Punch. Whole villages were burned down and innocent people were massacred. Reports reaching Srinagar were not allowed to be published in the Press. No official reports were issued to allay the fears of the public.
This happened in September and the tribesmen did not enter the State before 23 October 1947.
Official Records of the United Nations Security Council, Meeting No:534, 6 March 1951, pp.3-4: (statements of Prem Nath Bazaz, a Hindu Kashmiri journalist)