My husband believes it's acceptable to masturbate in front of our child.

I'm feeling really disturbed after what happened in the bathroom. I walked in and found my 4-year-old bathing while my husband was sitting on the toilet touching himself and watching inappropriate content on his phone. I find this behavior incredibly troubling, yet he seems to dismiss it as insignificant. When I confronted him about doing something inappropriate in front of our daughter, he responded with, "It wasn't a proper one." I’m unsure how to handle this situation. I'm feeling repulsed and worried that this may not be an isolated incident.