Former Nixon White House counsel John Dean appears before the House Judiciary Committee today to describe the progression of events of the Watergate scandal and their (rather obvious) parallels to obstruction of justice efforts by Donald Trump and crew today. In 1973 Dean testified before the Senate about the crimes and cover-up, and Nixon's involvement; he served four months in prison for his own role in those crimes.
Naturally, Donald Trump is enraged by this. And naturally, that means broadcasting insults on his shipwreck of a Twitter feed.
Trump has not been coy in his praise for those that stonewalled investigators seeking information on Russian election meddling, Trump hush money payments, and Trump's still-hidden financial tangles. Similarly, he hasn't been coy about blasting all those who do cooperate. Former Attorney General Jeff Sessions found himself on the outs with Trump for not shutting down the investigation into Russian hacking before it began; later hire Bill Barr, on the other hand, has been getting bubbling reviews from Trump for leading a new effort to block Congress from obtaining any of Mueller's underlying evidence, Trump's financial information, or executive branch testimony.
John Dean was a key figure in exposing a then-sitting president's personal efforts to obstruct a federal investigation, which no doubt counts in Trump's mind as one of the very worst things a person can be. Expect him to be fuming about this for days.