I have been struggling with this question for some time now, and i still have no clear position on it (I never said I have all the answers). But would like to share some of my thoughts on the subject.
I understand the fears of some for arming the opposition and the FSA, that arming might start a civil war in Syria and no one will be able to put down the fire then. And this is a valid point and if one is not scared of this possibility then he is not taking a fair full look at the situation. A second valid point I think is that FSA has no clear central command, so which group are you going to arm. The fear will be each party (external parties or internal living out) will arm the fighters that agree with their ideology, so you will have some arming the Islamist and others will arm the leftist or the nationalist and so own, so you will end up with a situation where the better armed fighters will win more battles and they will push their agenda on the other fighters and later on to new political system after the fall of the regime. Or you will have internal fighting between fighters themselves who are armed by different parties.
On the other hand, rebels and defectors are fighting the regime already, so no point of denying that fact, and one can argue that they are the last hope for many Syrians on the ground to topple the regime. So far no valid political solution is presented for people to hope for with no need to carry more arms, in fact it looks more and more that the regime do not feel threaten at all, therefore doesn’t seem to be really interested in any negotiation or a political solution. It can be suggested that if defectors are armed better and presented a real threat to the regime then regime will respond to political initiatives in more positive manner and you might even see more defections in army which will shorten the period of its fall.
In the end of the day, opposition should lead the way not be lead by the people on the streets, they should use their knowledge and intellect to take the hard decisions which can’t be popular all the times (otherwise anyone can do the job of echoing what people are saying). It is evident that Syrians on the ground are calling for arming fighters out desperation since they are the ones who are getting killed and bombed and starved. while most of the people calling for a pause and think are coming from opposition living out with not as much to loose (exceptions always there for both). I think a middle ground is to arm rebels to the point that they present a real threat for regime to sit down and really negotiate, while organizing the FSA under one command with Syrian agenda in case more arms are to be used.
Standing still and waiting for the best is not an option at all, and waiting for the west to decide to intervene is a stupid strategy, we should not be part of their strategy or interests.