I see both sides of this argument. HOWEVER, there's no doubt this card is a bit too ridiculous. The effect itself is fine, but it can't be destroyed? Now, com' on. That makes it rather unfair and makes the game play very lousy.
In my opinion, there are way too many cards that can't be destroyed in this game. We need to limit such cards, or it takes away the whole point of card games like this, which is the "exchange of moves and techniques." OOPS, SORRY, BUT YOU CAN'T TOUCH THIS CARD isn't not going to make a good game. It only makes one of the players feel superior or egoistic. A game is meant for "two people" to enjoy.
So, I say keep the effect, but take away its immaterial status.