it's kind of silly to get muted for expressing a valid point of view because someone else didn't like how you phrased it

The problem here is that you started out rude without actually making a point. Why should flagamuffin bother to respond? You haven't given anything valuable as input yet. You didn't "express a valid point of view", you straight up insulted the other person for something that you don't even know they believe. The discussion has nowhere to go after that but down.

Start with a well-reasoned contradiction. Start with "Millions of people eat it all the time and we aren't walking around with brain damage akin to taking a career's worth of hits in the NFL." Start with "That article is not well-researched and it uses poor science and scare tactics to drum up something you would see on Fox News." Don't start with the equivalent of "You and your opinions are stupid". It's not conducive to polite discussion. It's clearly unacceptable.

More to the point, what sort of conversation were you trying to create with that comment? What positive reaction were you hoping for?