This card does not work for me when it is attacked. There is no effect blockers active and parasite paracide flips over then goes straight to my graveyard instead of my opponents deck.
But that's not how other flip effects work. Look at the flip effects that summon creatures like bubonic, you 🔥 it, it flips and summons another bubonic from the deck. Doesn't seem fair to me.
No, if a card is destroyed by battle, it can't go anywhere else but to the graveyard, unless it's effect explicitly says so. Plus, flip effects that cannot have all of their listed effects accomplished, won't activate at all, as you might have already noticed with Dark Cat with White Tail being flipped alone by an attacker in the player's field. If he'd survive, he could be a target.
Well that is simply false. As I said in replies above, the official Konami ruling for this card is that flip from combat activates the effect and it goes to the opponent's deck even if it would have otherwise gone to the graveyard.
"If "Parasite Paracide" is flipped and destroyed by battle, the effect activates, but the effect is not applied. (It is not shuffled into your opponent's Deck.)"
https://yugioh.fandom.com/wiki/Card_Rulings:Parasite_Paracide