Am I wrong for telling him to block her?

For the past few weeks, I’ve been seeing this guy. It started off as just sex. Like a friends with benefits type of thing but he asked me on a date and we get along really well. I really like him. But this girl he used to date is still hung up on him. She was at the park where we were on our first “date” and came over talking trash about me saying I was ugly and he downgraded. He stood up for me and said that the way she talks about people is partly why he doesn’t like her anymore. That they don’t vibe right and he doesn’t like her personality. But she’s always calling him and texting him. He ignores her and rolls his eyes but I don’t get why he doesn’t just block her number. Every time she says something, whether it’s through the phone or in person, he entertains it instead of just blocking her or walking away from her. I’m the type of person who avoids that kind of stuff because I don’t need that in my life. I don’t need people who just act so rude like that. So after she said something to him at lunch today (we’re in high school so that’s why we see each other so much) I told him that if he doesn’t block her and tell her to just leave him alone, I can’t be with him. It’s seeming more and more like he’s the type to go back and forth between girls and I’m not the type of person to mess with that. It’s a shame because I really like him but this is getting too much for me. I’m really trying to work on my mental health and surrounding myself with only positive people so this situation is kind of messing that up.