Claiming to filter at lights for safety reasons is even less credible then the loud pipes save lives argument. Stay in gear, watch your mirrors and always leave yourself an out.
Filtering/splitting comes down to one of the key reasons for most of the crap driving. Selfishness. Meeeeeeeee Fiiiiiiiiiiiirrrrrrrrrrrrrssssssssssst!!
I am sorry Sir, but it is not necessarily selfishness. When I drive my car I have no such urge to get in front whatsoever, I follow all the other traffic, as my vehicle occupies a good portion of the lane I am travelling onto.
With the motorcycle on the other hand there are several valid reasons to filter to the front at a traffic light:
1) My vehicle uses much less space than a car/van; having motorcycles dispersed in traffic with each taking as much space as a car makes city traffic congestions much worse than they normally are.
2) My vehicle accelerates and brakes much, much more quickly than cars/vans, which allows me to move out of the way when traffic lights become green, therefore once again making traffic movement more responsive, albeit by a small amount.
3) Moving at the front allows motorcycles to be static in traffic for an overall lower amount of time, thus lowering the chances of overheating, which is much more of a problem in motorcycles than cars, as some of them are air-cooled, others are liquid-cooled, but with an overall heat exhanging mass smaller than cars in proportion to the engine displacement. Motorcycles are not designed to be stuck in traffic for prolonged time, certainly not as much as cars anyway.
You see, being a sports-bike rider doesn't necessarily mean being a selfish, ego-centric speed maniac.
Regards,
Frio