Is this rude what he said to my kid?

Verge of complete break-off/breakup. Been with my boyfriend for over 2 1/2 years but things have been rocky lately. I have my 3 year old son from my previous relationship. We live here with my boyfriend for a year now. (I still coparent with my sons dad) My son is wild sometimes as all kids are, curious and like to explore. Hes 3, hes active, sweet, nice, has tantrums, all around typical year old. Well we were relaxing on the couch laying down before we go to work after cleaning and getting stuff done this morning. My son fell off the couch after climbing on the side and my boyfriend immediately got up and said “thats what you get!” And then “im looking at you!” While my son was crying on the floor and ran away embarrassed. I told him to not say that to him again because its not effective in helping him learn and just makes him feel bad and he just said “ok as he was turned away” thing is we had a convo about breaking up and he walked away then too (hes avoidant) after this i just feel really done. Im in my cut off toxicity mindset, i just found it so rude. Its not like he has the responsibility of my child, he doesnt even spend much quality time. Not that hes required too but he just sits around and focus only on himself in his free time. Then gets annoyed when my kid is just being a kid. And doesnt know any parenting methods. His mom is toxic. I also grew up with toxic parents. Im doing my best as a “single mom” and my boyfriend/ soon to be ex is not helping.