Burke may have intended (it's not clear) that he would permit the gay son or daughter to come to family gatherings alone.  There is no sense in which that is less despicable than excluding him/her altogether, or excluding the couple.  It absolutely constitutes shunning -- and Burke, who has no children, is recommending it to people who do.  It's filthy advice.  I don't think many people take Burke or people who hold views like his seriously, but sadly, I'm sure some do.