Maybe the reasons teenagers use these devices is because we're told by society that we aren't allowed to know what we are talking about until we have a college degree and a few years under our belt. Maybe all this pressure is too much. Maybe I want to voice my opinion but am not willing to. Not because I am stupid, but because I know there is always someone, someone like Mr. Mali, getting ready to cut us down. We will speak up when you learn to give us room to be heard.
I don't think Taylor Mali is trying to cut teenagers down with this poem. In fact he's really talking about how today's generation, which includes my generation too by the way (I'm in my late 20s), does not speak with conviction and authority because we try to soften our speech with upward inflections, "you knows", "likes", etc. in order to sound more agreeable, but it ends up just sounding very passive instead. So when you say "We will speak up when you learn to give us room to be heard", I think Taylor Mali would disagree and tell you that you should speak up and MAKE the room hear you with the conviction in your voice rather than waiting for anyone to give you permission. I think that's the real point he's trying to make.