An Exclusionist, also known as an Exclus, Exclu, or Reactionary Exclusionist Gatekeeper (REG), is someone who attempts to gatekeep the LGBT+ community by claiming that certain groups aren't "really" LGBT+ based on their own definition. The term includes TERFs, TEHMs, truscum, enbyphobes, aphobes, biphobes, multiphobes, and ENM (ethical non-monogamy) exclusionists.
This falls under the queerphobic umbrella.
How exclusionism is harmful
Exclusionism is harmful, not only because it ignores what being LGBT+ means, but also because it leaves out essential groups and invalidates the harm and lack of representation done to other members of the community. Many exclusionists believe that to be LGBT+ you have to be severely oppressed. While this is how the LGBT+ community started, it is not what defines the LGBT+ community, as not all individuals of a certain sexuality, gender, or relationship type are oppressed to the same extent.
The LGBT+ community is a space for anyone who is not queern't, whether oppressed harshly or not. The LGBT+ community is supposed to promote diversity in sexuality, sex, gender, and relationships, which by nature includes a-spec, non-monogamous, and any other queer identities. So long as they are lacking representation and validation in media and everyday life, and are safe and consensual, they are LGBT+.
E.C.L.I.P.S.E. (Education, Culture, Language, Intelligence, Preservation, Sexy, Exclusionist) is a term some exclusionists use for the "exclusionist community."
The flags were coined by Twitter exclusionist @tomnooksfatass.The three main flags used by E.C.L.I.P.S.E. are the eclipse flag, which represents all exclusionists, the solar eclipse flag, which represents man- and masculine-aligned exclusionists, and the lunar eclipse flag, which represents woman- and feminine-aligned exclusionists.