Who insisted that no atheist could possibly have a true moral sense, since all morals were given by God. I kept trying to show him that it was possible to develop a sound, consistent system of ethics which did not reference God. I started with Aristotle, and continued with Jeremy Bentham and so on. He refused to accept it.

As long as you find other people's faith okay, too.

BTW, most of us Christians are motivated by empathy, too.

Suggest you read the SOP for the group; that should answer your question.

Live free!

and projects. Some of them include non-believers and some do not.

It seems to depend on what their objectives are.

If they are clearly religious, then tend to include just religious groups. If more secular, they tend to include others.

And I think the social justice messages are better than anything we atheists have come up with

I think liberals and progressives in general share the same values when it comes to social justice. It would make no sense whatsoever for us to exclude either believers or non-believers.

Those that attack theists or atheists are divisive and do nothing to further their shared agendas.