Er... for one thing, if lasers just filtered out everything but the light going in one specific direction, you'd need a 75w lightbulb or more to get as much power as is in one of those little pen lasers, and they'd make damnably poor weapons. There's generally a good bit of focussing there, I believe. For another, since you'd be taking all the light from one direction (the size of the arc is neither here nor there right now), that'd mean there was a slight disproportion, with a little more light bouncing off the back of the generation chamber than the front. Not enough to generate a noticeable effect as far as movement goes (personally, I'd be more worried about being deep-fried, blinded, or irradiated, depending on the efficiency and generation type of the laser), but still technically some.
But with the exception of beams, none of the weapons in Freespace are likely candidates as lasers, and we've already assessed that beams wouldn't recoil.