. And as far as 501(c)(3) status goes none of these people fall within a protected class. A dojo will not loose it's non-profit status if they tell stinky guy to clean up or leave, or loud guy to quite down or leave, flirty guy to stop flirting or leave or opinionated gal to stop gabbing on the mat. However, a person's religious status is a protected class for 501(c)(3) purposes.
It all depends on the charter of the organization and if it was approved by the government as such. You cannot discriminate period.
The best case example is Boy Scouts of America...a 501c. The Supreme Court upheld there ability to refuse membership to homosexual and atheist individuals based on their organizational values. They can also exclude females membership as a "Boy Scout" or "Cub Scout".
They cannot, however, exclude anyone based on religion, creed, or ethnic basis.
They cannot also exclude adult members of either sex as adult leaders.
Yes, 501c3 can be restrictive as an organization, but it cannot discriminate per se.
So you can, for example have a "Christian Only" dojo. Or a "Muslim Only" or a "male only dojo".
But those parameters must be established based on a very defined criteria and it only applies to those categories as generally recognized as historic values etc, of the organization.
You can't decide though to not allow Chinese Muslims, or Japanese Females etc or change your views midstream, or show inconsistency.
You will also cut yourself off from funding sources, as the BSA found out with United Way and other organizations that did not support those BSA values.
However, in the case of BSA, you had plenty of religious groups like the Church of Latter Day Saints that supported the BSA that have provided a great deal of support, whereas, the Unitarian Church and the BSA pretty much went there separate ways.
But yes, just because you are a 501C3 does not mean you have to accept EVERYONE...it just isn't true.