Everyone thinks me and my friend are... you know...?

Not "just friends". It's a guy, but there's nothing but platonic frienship there. I don't find him attractive, and I'm sure he doesn't find me attractive either. I really like our friendship the way it is, and I'm tired of other people poking their heads in and making him feel uncomfortable. I personally don't care what they think because I know the truth. How can I get him to understand that I'm NOT trying to change things to a romantic situation, and that it doesn't matter what anyone else sees if it isn't there?