I'm not sure why people think the 1970s were so conservative. Nixon wasn't a conservative, Ford wasn't a conservative, and Carter wasn't a conservative. And with the exception of the 1978 election, there wasn't much GOP success to be had anywhere. Pop culture seemed pretty liberal too, from the Studio 54 to Charlie's Angels to Three's Company. Politically, we almost had the ERA, we got expansions in the Clean Air Act and the launch of modern day environmentalism, relations with China, and arms treaties with the USSR.
Probably due to Nixon's landslide re-election--a candidate losing for being too liberal was something new in the post-New Deal era--along with the beginning of the resurgence of conservative Republicanism, Carter being probably the most right-wing Democratic president since before the 30's, and other thing related to those phenomena. While left-wing activism was at its peak, the conservative response to it occupied the White House, and Carter was no New Deal labor liberal. That said, the actions of the Nixon administration, ironically, are one of the key points to the 70's being a liberal decade. He was a great example both of the electoral opposition to the perceived far left, and to the lack of any real direction for a conservative President to go in.
EDIT: Beaten by Lief.
