The immediate answer to the thread title is "Execute them", this is by far and away the most annoying thing - in my opinion - that someone can do in a race. I mean, it's not like it takes a large amount of skill, judgement and experience to get the car to move when the lights go green.
Despite that there are sometimes legitimate reasons for this - as Dru points out, for example, controller issues - if it caused an incident, I would still be leaning towards reporting it. By all means put in the report that it is a low-priority thing, so as not to waste important admin time, but if the driver in question lets such things happen often, the admins should be able to notice - perhaps in licence notes.
There's only one excuse for doing this, and that's lag. If you try your utmost to get out of the way and the system does not permit it, then - unless you're running torrents or something - fine, it's unavoidable, and not your fault. But, the rest of the time, even if your controller dies (or something else prevents you getting off the line) that's what God gave us the "Shift" and "S" keys for.
Those who wander off and aren't even at the 'wheel when the lights go green should probably be subject to my original suggestion.
My opinions on the matter, anyway.
Sam
