Lately, it has become fashionable among liberals in America, following CIA director Porter Goss's not-so-cryptic remark saying "part of the difficulty in capturing bin Laden was sanctuaries in sovereign nations.", to encourage the invasion of Pakistan (via Patrix), or at least inquire of the Bush administration why, if the Bush doctrine proclaims that "the U.S. would make no distinction between the terrorists who committed these acts and those who harbor them", is Pakistan not being given the same "preferential" treatment meted out to Saddam Hussain's Iraq.
First of all, I think liberals, when they adopt this stance, would be prone to accusations of hypocrisy. You cannot condemn the invasion of one country and encourage the invasion of another at the same time. I think one objective liberals have in taking this stance is to point out the Bush administration's hypocrisy in this. But they need to take care not to push the administration too much, which might actually consider these war cries from liberals as a free pass for the next military backpacking adventure, be it Pakistan, Iran or Syria.
The second, more important reason is this : The reason Pakistan should not be invaded is the same reason Iraq should not have been invaded in the first place : Even though both are / were being ruled by undemocratic dictators, both are / were instrumental in keeping the islamic fanatics in their respective countries in control. Remove Musharraf and be prepared for permanent instability in the region, akin to the chaos reigning in Iraq, except it could be exacerbated into a nuclear holocaust if Pakistan's nuclear weapons were to fall into the hands of these fanatics. And as we all know, when the US invades a country, rounding up and controlling WMDs / conventional weapons stockpiles are not the first thing on it's mind, as compared to, say, whats the word I am looking for, .... oil. India and every country in the subcontinent should strongly oppose any such inclinations by the US. Hopefully, the US won't make the same mistake it made when it went into Iraq and try to willy-nilly remove dictators it deems to be undemocratic.