One problem with "since the 60's", JFK was a hawk, his brother Bobby was even a bigger hawk.
Both the Democrats and Republicans were anti communist and pro military. During the Presidental election JFK vs. Nixon it came down to who would do a better job at stopping communist expansion in the world ?
It wasn't until 1970 when radical leftist (The New Left) began coming under the Democrat tent and first they hid behinde the "liberal" label when you started seeing anti-military and an anti war movement against any war that would be fought against communism or any form of socialism with in the Democrat Party.
It was during the 1970's when the true liberals with in the Democrat Party started leaving the party and came under the GOP tent, they were called neoconservatives. JFK Liberals who were anti communist and refused to surrender during the Cold War.
Now not all liberals fled from the Democrat Party. There still were Democrats who refused to surrender and wanted to continue fighting the Cold War. You had liberals like Rep. Charley Wilson (D-Tx.) who remained in the Party. Yep the same cocain sniffing, skirt chasing, partying Democrat that the movie "Charley Wilson's War" is based upon. The same liberal Democrat who got Congress to support the Mujadeen in Afghanistan by arming them with Stinger missiels.
History rest it's case.