Teller may have gotten a bit loony later in life, but he was right in the need to develop the bomb. A world with the 1950's Soviets with the bomb and us without would not gave been to secure.
MAD worked. We did not go to war with the USSR.
Teller was one of the influential voices that convinced Reagan to launch Star Wars.
The panoply of new weapons systems dazzled Russian war planners. In the end, they told the Politburo to sign the treaties and end the Cold War or the USSR would go bankrupt trying to counter SDI.
Teller was right both times.