There will always be pilots that do dumb things.
So, based on anecdotal here-say, you'd like to prevent
the rest of us from competing, or make it unpalatable ?
Really now...

The story was not here-say. It was an eyewitness report
from a pilot who was next to the runway when the motor
glider landed. He even said that although he was standing
less than 300 feet from the runway and there were runway
lights on he didn't know the glider was on the runway
until he heard the wheel chirp on the asphault.

Give them an inch and they will take a mile. You motor
guys weren't happy just being allowed to enter competitions
with non motorized gliders. Now you not only want to deny
there are any advantages to motor gliders. But you want to
claim you have disadvantages and want even more concessions.

Eric wants to be able to get airport bonus points for not
landing at an airport worth bonus points. He says it's
safer for a motor glider to start his motor and fly away
rather than land for airport bonus points. He claims
that at Coulee he gave up the airport bonus points by
starting his motor in order to make it safer for other
gliders. I guess we should assume that the fact that
the runway is only an 18 foot wide gravel runway, had
no bearing on his decision.
http://www.airnav.com/airport/WA15

If you want to compete with non motored gliders in
competition, at a minimum you should.

Launch by aerotow
relight by aerotow
be scored to the last turn completed if motor is used
land at the airport to get that airports bonus points

Soarin (motorless)