Ouch! Exclusion is such a harsh word. What place could it possibly have in a world that's open, inclusive, and thrivable?
Like a hammer, exclusion is merely a tool. In its unhealthy forms, exclusion is used to oppress, to avoid accountability, circumvent democracy, and maintain established economic and political order. It brings to mind secret societies, smoky back rooms, nativism, and dehumanizing the "other."
But exclusion can also be healthy and life-affirming. For individuals, that may mean choosing your conversations more wisely, lightening your load, de-cluttering your mental and physical space, eliminating distractions and focusing on what matters most. It means making space for solitude, contemplation, attention to yourself, to your breath, to nature, to being fully present.
Exclusion is not a choice of whether to exclude, or not, it is a choice of what 
to exclude.
For groups, healthy exclusion means creating safe containers in which to share and collaborate more deeply. It means being intentional about who and how many you want to share space with. It's about creating and protecting sacred space. A good host has a talent for appropriate exclusion. It's the social artistry of choosing who you want at the party, and who you don't.
Every marketer knows that exclusion is a powerful tool. Done well, limiting access to a place, a group or a product makes it cool. Anyone who has launched a new online community can tell you that early on exclusion is vital -- to set the tone and model the kind of interaction you want. It's a way of establishing a new culture intentionally.
Exclusion can be about useful constraints, which spur creativity, whether you're answering an essay question on a test or innovating new products. Imagine, for example, a candle. What is a candle without a wick? Without light? Without heat? Without wax? Such a thought experiment can help you identify which properties are intrinsic to something, and think creatively about novel ways to reproduce them.
Exclusion is part of evolution, particularly the conscious evolution we are living through now. It's about casting off outmoded, destructive ways of thinking and being. And it's absolutely essential to a thrivable future.