It seems that there were three, now a fourth sexual tribe has developed, the poly's. These sexual groups behave like tribes; they are hostile to all other groups. Gays, trans, mono or normal's, and now the poly's.
The human animals do not throw true to our sex, some have physical issues, other have psychological based sexual issues. Others are just never satisfied. Mono relationships are likely the most common, and are the most likely to provide healthy mentally balanced children. Poly's cause many family separations, and I cannot see how they can not cause jealousy, or lack of caring about the offspring, lack of support of questionable offspring and similar issues.
The poly goes around hitting on every one they feel attracted to. They cause much resentments, and much distress and unwanted effort to rebut. Some of them are far too pushy, and need to be publicly shut down. Their behavior can be discussing, even repugnant to normal mono's.
Those who are beyond reproduction age only have relationships to be concerned about. But since these appears to be tribal like, anyone jumping between tribes can expect that some will not be happy about across tribal communications. In other words, when a parent becomes poly, they may lose the respect of their children, and also the attachment of the child.
A skeptics/atheists do not want our time, devoted to the study, to be wasted or diluted or wasted with poly perverts promotion, and took steps to ban a waster who is promoting poly rather than the study of atheism. There mistake was to publicly state the ban, rather then privately.
Whether the hitting on was real, innuendo, or imaginary, unwelcome hitting on the prime organizer of the event may have caused a overreaction, and as a result they became 'person non grata.' Together with a bunch of complains from the previous year for time wasting on non advertised subject, decisions were made to not only not invite him as speaker, but to outright pan the individual. Oh well, there are always issues in organizations. Splits will occur. It is time to move on, but not in the USA. Sue the offender, and destroy the organization and the prime organizer.