"Propaganda is a form of communication aimed towards influencing the attitude of the community toward some cause or position by presenting only one side of an argument. Propaganda statements may be partly false and partly true."
Get educated
Whether or not he was spreading propaganda does not mean you should act in an unprofessional manner. You represent your product/currency, remember that. And no matter how justified you feel about lashing out, sometimes it's better to just keep quiet.
Telling someone to "GTFO" or "Get educated" may not seem like a big deal, and in most cases, they're not. But that sort of lack of professionalism is definitely something that makes me think twice about investing or mining your coin.