I hope we played this right - Heaving Swing let's Cragheart push a monster into an obstacle. If you do so you destroy the obstacle and the monster suffers 2 damage. I did this to a Living Spirit but as I read the card the flying ability has nothing to do with not being able to activate the ability. If it was a physical monster I'd assume he pounds it into the rock, it only seems a bit weird because it's a spirit...
Did we play this right or wrong?
The wording as is is going your way.
But I'm pretty sure having seen a FAQ entry or thread that says that flying monsters don't take dammages from exploding obstacles.
I can't find it and so I'm not sure.