IA clearly believed this was fair use and I’m sure can demonstrate reasonable grounds for that belief. Even if the plaintiff’s lawyers can make a stronger argument for it not being fair use (they probably can), that doesn’t negate the existence of IA’s grounds.

Here’s a story about weak but reasonable grounds: Say I think it rained last night because I glanced out the window in the morning and saw the street was wet. You say it didn’t because you got up earlier than me, saw everything was dry, and you saw a street cleaner come through, making the street wet. Clearly you’re right but before I had this information, I had reasonable grounds for my belief.