When anyone joins the humanists, they are not required to renounce their religion, but many of them do. Some of them continue to claim to be Christians, Jews or whatever religion they used to be, while others proudly proclaim they no longer adhere to any religion.
There are even some who go back and forth, claiming the protections of their former religion, while renouncing their adherence to it. They will claim to be Jewish when they see real or perceived persecution of Jews, so they can instantly claim victim status. Then they say they aren't bound by Jewish teachings, because they aren't really Jewish. Then they will represent themselves as Jewish again, so they can show that Jews support humanist propaganda. Other religions get bastardized this way too.