Is AUTHOR wrong in the post ? POST : I really can’t tell if I was being too insensitive or not. 

A few friends and I were invited to play some touch football at the beach one day with some random people we met who were throwing around a football. After a while we were getting out of breath from all the activity and one of the guys made a joke saying something like “I’m going to end up tearing my other ACL.”

He talked a bit about it a bit later on telling us how he tore his ACL in high school and how it sucked.

After a while of playing, we all getting very tired and almost falling over. I ended up tripping myself out of fatigue when running for the ball and said something along the lines of “I better watch out or I’ll end up tearing my ACL.”

After saying that, the guy who tore his ACL started to criticize me about how tearing an ACL is a serious thing and shouldn’t be joked about.

I understand tearing an ACL is serious but this guy seemed perfectly fine playing the game and I thought it wasn’t too serious of a thing for him since he was making a joke about it earlier. AITA?