Robert F. Kennedy‚ Jr. responded to former President Trump's allegations he is a &;quot;Democrat plant&;quot; and would be a &;quot;wasted protest vote‚&;quot; challenging the presumptive Republican presidential nominee to a debate.  &;quot;When frightened men take to social media they risk descending into vitriol‚ which makes them sound unhinged‚&;quot; Kennedy wrote in an X post on Saturday afternoon. &;quot;President Trump's rant against me is a barely coherent barrage of wild and inaccurate claims that should...