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, and multiphobes.
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 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.