If the four corners report from last week is anything to go by:
1) The local security forces can't necessarily be trusted
2) We are there in part due to a political fix by Tony Blair, to promote the 'good war' given the unpopular decision at home due to the iraq invasion.
3) Our current solution may be to negotiate with the Taliban even though the original war was to remove them I thought.
4) Oppressed groups with guns will seize any power vacuum left by a dictator.
I don't even think a term like "Home support for the war is decreasing" has any more weight than "We are 100% behind the troops", it's a propoganda term to stifle discourse on the real issues. Hopefully our leaders have the courage to make the right decisions involving the war and our troops. Claims like 'it's too costly' are a little bit late given we have now decimated a country.