Transport ramming, when done properly, is very, very safe for the rammer.
The key to effective transport ramming is to catch the enemy vehicle in a position granting him limited maneuverability - for example the offices near silo 5, the bridges going out from the central silo, any place where there's no place to run.
The second important thing is to catch the pilot by surprise, preferably by attacking from behind.
The third is choosing the right altidude. Low altitude means slow descent, meaning easier aiming, as the vehicle will "sweep" a larger area. High altitude means an easier and sneakier approach, but requires better aiming, as the transport will drop on a limited area.
For the record I never initiate transport ramming, but when any hostile player breaks this convention then my assumption is that it no longer applies to this game.
After all, common courtesy of war is - "We both have NBC weapons, but you don't use yours and I won't use mine."