Red flag?

Is it a red flag if a guy you just started talking to tells you to block his ex on every social media etc.? Apparently she still had his Facebook password and saw that we had called each other a couple times on the app so she started texting him asking who I was. He calls her crazy and says that she started calling me all types of names so he told me to block her before I got caught up in all the drama. Does that sound believable, am I being too untrusting?