I doubt there is any way to stop any age group from posting here. How would you know?
As to lowering the voting age, my position is the vote should be an earned right. You should be required to give something back to the nation before being afforded the right to vote.
Military service would be one route.
Perhaps civilian service akin to military service (i.e. park service or some other real work).
Or proof that you have been a PRODUCTIVE member of society (aka pay serious taxes and show you have WORKED for at least 10 years non-stop).
I believe this would eliminate the leaches that are voting themselves pork at the trough.
(sigh). I can dream can't I?