A friend and I ordered a delivery pizza to split, we paid for it equally. When the pizza arrived, I ate 3 of my 4 slices, and my friend ate none (4 remaining). The pizza was then left out all night and for most of the next day. I am perfectly fine with eating pizza that has sat out over night(I'm aware of the health risks involved, but it has never given me problems), my friend however is not, and was upset that I did not put the pizza in the fridge, which resulted in him throwing the rest away.

He insists that there was a 50/50 responsibility for either of us to put the pizza away, where I insist that I had 0 responsibility due to having less stake in the pizza remaining, and for the aforementioned fact that I was fine with pizza that sat out. A very long discussion was had over whose responsibility it was. Am I the asshole here for not putting the remaining pizza away?

Additional information: we had this pizza delivered to the Airbnb we were sharing, so we were both sleeping at the same place. The friend was aware that the pizza had arrived, and was present during this.