There is very little chance Yarvin would get past the HR department of any client I can think of, are there professional environments you can think of where his reputation wouldn't cause significant difficulties to participation?
I'm not sure an argument from professionalism is the appropriate one. More if you have a club you can invite whoever you like, and if others are not comfortable with the members they can choose not to attend.
I'm sure John De Goes is earnest, the risk is that his conference may be attended solely by similarly earnest people who look precisely like John De Goes, and for whom emotional assault is unverifiable and incomparable, hypothetical.