Ruling on the Whip

Brian

and I

Met for Lunch at Veggie Grill in Irvine for some Magic: The Gathering & some trash talking

We also talked work & started gearing up for NaNoWriMo

Brian has a lot of cards in his bag

I am still running a very simple Rakdos deck

Brian has been crushing me lately with a UW Deck--it Mills, it has Planeswalkers, & it has some white creature spamming

We did have a tricky rules situation come up again. Brian was milling me and I had like 10 creatures in my graveyard so I attempted to use the Whip of Erbos

to pull a Gray Merchant of Asphodel out of my Graveyard

doing four to Brain. 

He attempted to respond to the Whip with Cancel

but I argued the Whip was using an Ability not a Spell. Brian agreed & took four--but I have no idea if this is the correct rulling.

We then we had a discussion about if there was any way to prevent the Whip from returning the Gary and causing damage. So, this weeks question, is mostly about "is there a difference between 'enter the battlefield' effects when a creature is cast as opposed to manipulated by some other Ability"?