Surely he must’ve known the Eastern Bloc existed for pretty well three decades at that point? What was the political motivation behind this statement?
Ford said this while responding to a question from one of the debate moderators that suggested that his administration's policies of détente were allowing the Soviet Union to increase its power at the expense of the United States. (Here is the debate transcript.) The moderator, Max Frankel, specifically brought up the Helsinki Final Act, which he characterized as "virtually... an agreement that the Russians have dominance over Eastern Europe." The Helsinki Final Act/Accords/Declaration, which Ford, Brezhnev, and the leaders of all but two European countries (and also Canadian PM Pierre Trudeau) had signed the previous year, affirmed the principles of territorial integrity, non-interference in internal affairs, human rights, and peaceful international cooperation. Frankel's question channeled hawkish criticism that the Helsinki Final Act granted the Soviets a propaganda victory and enshrined the Cold War division of Europe. Ford was arguing clumsily that by signing Helsinki, he had not granted legitimacy to the Soviet domination of independent Eastern European countries.
Although Helsinki came in for criticism in the United States from Eastern European immigrant communities and ideological foes of détente -- invocations of Yalta and Munich, etc. -- it provided an important impetus for dissident movements in Eastern Europe and for the international human rights movement as a whole. For example, the Charter 77 declaration, a milestone in the history Czechoslovak dissent, criticized the Communist regime for failing to uphold the civil and human rights affirmed by the Helsinki Final Act. Ultimately, Ford would characterize Helsinki as his "finest hour," but he failed spectacularly at defending it.