1. He thought she'd be foolish enough to share it without listening to it first
2. The song didn't have that line originally, but he added it after Taylor's refusal to help him promote the song
Honestly, if she wins on Monday, I hope she gives a nice speech that doesn't mention him at all until the end where she finishes it with this line from Tupac: youtu.be/41qC3w3UUkU?t=4m29s
I'd love if the Grammys this monday would turn into something like 2009 CMA Awards where everyone was shading Kanye and Taylor was reaping her gongs throughout the night.