I am not in the US. I have decided for myself on the basis that (i) the first word of the tweet I linked is a nasty ethnic slur and (ii) its contents are merely schadenfreude over someone's raw emotional outburst in response to a traumatic event. There cannot be a good reason to invite such a person to a conference except to send a clear signal about what kind of person is welcome there. I think you know all this, which is why you respond in such an oblique manner.

I'm pretty sure all kinds of people are welcome there. I don't approve of the guy's tweet, but I also do not limit myself to groups of people that share the same views as me. Take the good, ignore the bad. There are some remarkable people there.