Flicker the brakes way before the corner to 'wake up' the drivers behind you. My personal experience has shown that this helps, but doesn't guarantee anything. There isn't much you can do about 'dive bombs'.. especially on T1. If you slow down you get run into, if you keep pace you usually run out of room and either put yourself or someone else (or both) off. Don't get too frustrated, it happens to us all, and happens quite a bit in 'real' racing as well.