Decided to do a little research based on one of the names in the article.
Jamaat-e-Islami, the group who organised the protest and presumably created those charming banners, are a social conservative, and Islamist political party. Its objective is to make Pakistan an Islamic state, governed by Sharia law. It was founded in India but moved (?) to Pakistan after Indian independence.
In Pakistan, The party came under severe government repression in 1948, 1953, and 1963. In other words, presumably because the leadership in Pakistan were not in favour of their aims, but later during the early years of the regime of General Muhammad Zia-ul-Haq, they served as the "regime's ideological and political arm". So suddenly they found a political leader open to supporting them.
Who is General Muhammad Zia-ul-Haq? He was the sixth President of Pakistan from 1978 until his death in 1988. Aided by the United States and Saudi Arabia, he systematically coordinated the Afghan mujahideen against the Soviet occupation throughout the 1980s. He rose to power following a coup and the removal of Prime Minister Zulfikar Ali Bhutto from office.
The United States, notably the Reagan's Administration, was an ardent supporter of Zia's military regime and a close ally of Pakistan's conservative-leaning ruling military establishment. The Reagan administration declared Zia's regime as the "front line" ally of the United States in the fight against the Communism.
Many of Pakistan's political scientists and historians widely suspected that the riots and coup against Zulfikar Ali Bhutto was orchestrated with help of the U.S. Central Intelligence Agency (CIA) and the United States Government because United States growing fear of Bhutto's socialist policies which were seen as sympathetic towards the Soviet Union.
Former U.S. Attorney General Ramsey Clark widely suspected the United States' involvement in bringing down the Bhutto's government, and publicly accused the United States' Government after attending the trial.
So now we have a bit of an insight as to how a fringe, far-right fundamentalist political party was able to gain a foothold in Pakistan.
Quite a web, eh? Politics, intrigue, double dealing, coups, CIA, Reagan.
But of course it's only about religion. A lot of posters here have it figured out.