Those who are saying nay to this issue need to realize that teaching arabic has a long term positive impact on the issue of militancy and talibanization in the country.
Currently, Pakistan is afflicted by a situation which is well described by the urdu proverb "Neem hakeem khatra-e-jaan, neem mullah, khatra-e-imaan".
There are many semi or half literate mullahs running around in madrassas and masajids who may be huffaz or know part of the Quran, but they are neither scholars nor those who can study this religion of ours. With most of the Islamic history still confined to pages of arabic literature, our rural population remains vulnerable to the fancies of these need mullahs who have been appointed imams on the basis of their beautiful qirat (recitation) or for some other reasons.
If Arabic is offered early on as part of a national curriculum along with Urdu and other regional languages, it will help. However the curriculum has to be more serious.
It is quite interesting that nobody knows anything about how life was in the times of the height of the Islamic culture. What the cultural issues were, what the social issues were, either we get a blanket sweep of "everything was fine" or just the issues from the standpoint of Islamic jurisprudence. Yet there are arabic texts that for an example, talk about the way the beggars lived in the streets of Baghdad and many other cultural and social issues that are only available to those who have an interests and are current with classic (fusha) Arabic. The rest of us have been deprived of this opportunity to read up on the past because we are Arabic illiterate.