It is clear that the need to socialize, the need to have a cohesive group of people to belong to, also renders people within the group susceptible to manipulation. It makes the individual gullible and accepting of errant ideology just for the sake of being part of the group.
Initially this desire to belong developed by way of evolution as it made it more likely that the species would survive. Each relied on the other for various needs. It helped the survival of the species. Once our intellect developed it became clear to many that this strength was also a weakness allowing the group to be manipulated and subjugated to the desires of a few.
It is this quality about humanity, the need to belong, to socialize, that makes atheists just as gullible to manipulators as theists when meeting in groups. To belong individual atheists will accept that some things that are clearly immoral are moral. That you must support certain groups despite the fact that doing so undermines civilization. It allows the acceptance of abnormal behavior as normal behavior. This is why many people label atheists as immoral… it is because they, many atheists, really have been morphed into an immoral mindset through manipulative forces.
It is only through constant vigilance that the individual atheist is able to remain aloof and wary of manipulators entering and attempting to undermine the group. Atheists+ was such an attempt by feminists to take over the atheist groups. It was successful in many groups including humanist groups which now are more or less controlled by feminist ideology.