Social Media, and the internet in general, gives everyone a voice. Unfortunately, omni-pricks, who's mission is either to make another person's life miserable or are SJWs who refuse to have level headed discussions, will make their shrill voices heard.
While I'm not a fan of his, I don't blame Joss Whedon for quitting the twitters. Would you want to spending much, valuable time out of the day blocking (or even having an assistant do it) users sending you hateful messages, with no discussion value? As fans and constructive critics have lost a method of contact with one of the major people behind the MCU, the only real winners here are the people who want to watch the world burn, and DC, to a lesser extent.