Why do people come in and act like the class is out of control?

I get really annoyed when another teacher/aide/anybody comments to the class when I am that class sub for the day and make it seems like they are just acting wild and out of control when I think it is actually going good. That happened to me today because the kids were chatty coming in the classroom from lunch and another teacher had their door open came out to tell them she been hearing them screaming and will tell the teacher. The kids were NEVER screaming or loud while in the class. Just dont understand why she made it seem like it was a bad class when they were actually great.