Why does Winston view the affair as a political act?

views his affair withas a political act
because every act in is political. Totalitarianism means that the
influence of the Party in every area of life is so pervasive that every word and action becomes
either orthodox or unorthodox: an expression of loyalty to the Party, or a rebellion against
it.

Sex may be permissible for the procreation of future Party Members
(Katharine, Winston's wife, had called it "our duty to the Party"). One should not
enjoy it much, however. This is because all enthusiasm and passion must be stored up for
politically orthodox activities, such as the hatred of Goldstein.

Although
Winston is the one who immediately thinks of the affair as a political act, it is Julia who
gives the best explanation of why it is a rebellion against the Party when she expounds the
connection between chastity and political orthodoxy:

When
you make love you're using up energy; and afterwards you feel happy and don't give a damn for
anything. They can't bear you to feel like that. They want you to be bursting with energy all
the time. All this marching up and down and cheering and waving flags is simply sex gone sour.
If you're happy inside yourself, why should you get excited about Big Brother and the Three-Year
Plans and the Two Minutes Hate and all the rest of their bloody rot?