I have found I can’t talk to any family about current events.  I am much better read, and not a great teacher - i have an authoritarian tone, i think.  i agree, respect his wishes to not talk about Q anymore — and try to find a way to enjoy your relationship with your brother.  you are dynamic and capable, and can find other things to relate about.  and while you do that, you can re-build credibility with him, and look forward to a day when your relationship can grow deeper.