Spirit Reaper vs Stardust Dragon/Assault mode

I recently had a argue with a friend about this two cards.

The situation:

He attacked my spirit reaper with his Stardust Dragon/Assault Mode.Spirit Reaper wasn't destroyed by battle,yes,but he said that he activates the effect of stardust to negate the activiation of the effect and destroy!

I would like to know if that is possible,i think that can't be made cause effect of Being indestructible in battle is a continuous effect,right?So it's not activated?

show this to ur friend Stardust Assault Mode vs Spirit Reaper

stardust assault mode cant negate a continuous monster effect like spirit reaper and marsmallon

Thanks