There are no secular Jews. All Jews are holy, because when the Torah was given at Mount Sinai, all Jews became members of a holy nation.

True, they have free choice to decide what they want to do, to say, and to think. But they can’t change who they are, and they are all members of a holy people. Holiness is the polar opposite of secular.

Sichot Kodesh 5738, Mishpatim, s'if 24.