Despite denials humanist and atheist groups hold ideologies. These are adopted credos, or beliefs, decided upon without any research, or sometimes even in contradiction to research. You find quite quickly when you attempt to join such groups that ideologies exist. If you are in disagreement with those beliefs, you are hounded until you either blithely accept them or leave the group. I have personally experienced these pressures, so I know they exist.
For whatever reason these groups adopt a perspective about certain issues, and that perspective is based on nothing more than preference. While spouting loudly about the merits of science, they nevertheless adopt perspectives that have no science backing them. When you ask for the science backing their viewpoint, they most often become angry and label you a bigot or worse.
Acceptance of a group is not based on science. Sometimes it is more based on compassion, sympathy, or empathy. Such acceptance does not need science. The error, the illogic, is claiming that there is science backing your preference… when there is none. More than one issue is held by otherwise reason-based groups in this way.
What irks me is the claim of backing by science, not that they hold these ideals. I share the perspectives of some issues, knowing it is only through compassion that I hold them. I do not claim science where there is none. It is the “human” thing to do.