How can we educators improve a lot of the negative behavior within the CS community
I reject a lot of the assumptions implicit in the question. Computer science isn't just for geeky or "smart" students. And I don't think it's fair to say that students in other classes are "more expressive, outspoken and creative." Computer science is full of art, creativity, and expressiveness. It's a teacher's job to show that to students and encourage every student to try it out.

I advise you to work on your own assumptions first. If the teacher thinks that computer science is not for creative students, then what hope do the students have?

Things to consider:


How are you "advertising" the computer science courses? Are you highlighting the artistic and creative aspects of it? Are you appealing to  students who might not self-identify as programmers?
What types of programs are you using in your lessons? Are they "boring" command line applications, or are they interactive and visual?
What types of programs are you assigning for homework? Do they encourage students to express creativity?


In addition to working on the assumptions of both your students and yourself, I'd also advise you to consider the needs of students from "non-traditional" backgrounds. More things to consider:


Are you "making room" for students who often get drowned out by louder or more active students? "We've heard from Grace already, why don't we give somebody else a chance to answer?"
Are you recognizing the work done by every student? I'd like to show you all a really creative example of how Ada used for loops in the last homework assignment...
Are you calling out bad behavior? Are you encouraging good behavior? Hey Grace, I know you know this stuff really well, so during lab today would you mind helping me out by answering Ada's questions?


These types of change have to start with you. I don't agree with a lot of the assumptions in the question, and I encourage you to take a harder look at some of the assumptions you're bringing to the classroom (which your students pick up on and perpetuate). Fix those, and you'll be able to help your students fix their own assumptions.