The officially stated UK government rationale justifying arming Syria's rebels relies upon at least two flawed assumptions.
The first is that pouring sophisticated weaponry into a war zone already awash with weapons will save civilian lives. Whilst this argument may have had some force when the army attacked unarmed demonstrators two years ago, Syria is now in a civil war in which two well armed sides have achieved military stalemate.
Western politicians often imply Syria's 70,000 dead have all been killed by the state, a picture further complicated by media quoted opposition activists counting armed rebel fighters as civilians. Estimates suggest security forces have suffered 15,000 fatalities, rebels 10,000, with the remainder being civilians killed by both sides.
Arming one side with better weapons seems unlikely to improve this situation - particularly when rebels have been repeatedly condemned, for example this week by the UN, for murder, kidnapping, torture of prisoners and civilians, use of child soldiers, widespread assaults and corruption against civilians, all without remedial action from the rebel Free Syria Army the West supports.
Rebel tactics of attacking and fighting from densely populated areas, itself a war crime, also inevitably result in heavy weapon use and civilian casualties - as now at previously peaceful Homs and Aleppo, as in the recent past at Gaza and Fallujah. Further arming the rebels will only increase such attacks.
Those advocating arming also assume that, because rebels are fighting a dictator, the rebels must themselves support democracy.
While opposition leaders outside Syria speak of inclusive democracy, gender equality and human rights, such concepts are largely alien to the Islamist fighters dominating Syria's rebels, the most influential of whom are groups such as the al Qaeda linked al Nusra Front. Rather, they aim to replace Syria Shia with Sunni power.
This is why the rebels are backed by Saudi Arabia and Qatar - sectarian dictatorships with no interest in promoting human rights or inclusive secular democracy. They do so to promote their own extreme brand of Sunni Islam, and because a crippled, possibly partitioned Syria isolates and weakens Shia Iran. This also promotes the interests of Israel.
Indeed, if Syria for the US and UK was about human rights and democracy, they would also be backing rebels in their Sunni allies Saudi Arabia, Bahrain and Qatar.
Some suggest that Islamist dominance of Syria's rebellion is reason to arm more moderate groups. As Arab Spring states are discovering however, 'moderate' is a relative term. And even assuming such 'good' rebels can be found to arm, doing so against 'bad' rebels is likely to cause civil war to continue well beyond any fall of Assad, with further appalling civilian suffering. In the chaos of civil war, it will also be impossible to monitor in whose hands such weapons end up.
There are two routes out of Syria's savage and indiscriminate bloodletting. One is an unlikely outright military victory, the other a negotiated settlement - and it is this option, by placing pressure on the rebels and their backers to drop preconditions to ceasefire talks, which the UK and US if seriously interested in peace should support.
Many have good reason to detest the Assad government. But this is no reason to provide weapons to those with little regard for democracy and human rights whose victory may benefit Israel and Saudi Arabia, but which for the true interests of Syria's people and the West may make matters very much worse.