I recently started reading a book about Sen. Joseph McCarthy, called "Senator Joe McCarthy," written by Richard Rovere and published in 1959. The book concentrates on McCarthy's reign of terror from 1950-'54, when he made many unsupported and never-proven accusations of the presence of Communist spies in U.S. government agencies and led a witch hunt for homosexual government employees that wrecked the lives of innocent people.
Already, one of the most fascinating aspects of the book is to see the ways in which McCarthy's way of operating presages Trump's. McCarthy lied all the time, about all manner of things; he sowed chaos and thrived on it; and he ignored conventions, personal and professional.
One big difference between the two men was that the chaos McCarthy engendered and the fear he fed upon sprang from a real source -- the threat of Communism and particularly the threat of the Soviet Union. The leadership of the Soviet Union was engaged in evil behavior -- mass murder of their own citizens, oppressive takeovers of other countries, worldwide spying and assassinations. McCarthy did nothing to hinder those evil actions, but a big reason that many more reasonable people -- like Pres. Eisenhower -- allowed him to operate with impunity was that the Soviet threat was real.
Trump has no similarly existential threat to justify his wild behavior. So it's a lot easier for people to call out his absurd, offensive and unstable statements and behaviors, as many do.
The similarity in style between McCarthy and Trump may be due to more than a similarity of character and purpose. A young lawyer, Roy Cohn, served as McCarthy's chief counsel. Years later, Cohn would become a lawyer and mentor for Donald Trump.
Cohn led the investigations of and attacks on government employees he and McCarthy identified as homosexuals. Cohn was himself a closeted gay man, and in 1986, he died of complications of AIDS.