It boils down to two things doesn't it? Would it make a difference, and/or should we be "doing our bit"
I'm not sure it would make a difference: it depends what the actual plan is. Extra bombing raids would not necessarily be advisable, or help, for various reasons, one of which of course being the "crowded skies" above Syria.
On the other hand, should we not be doing some of the work, and giving the others a "rest"
Of course, Dave can't really sell it as such: he has to push the "in Britain's interests" line harder than perhaps it ought to be pushed.
We definitely should not be looking to start fighting against Assad's forces. Syria needs, desperately, a ceasefire, and that would only make matters worse for the ordinary people.