There is a significan difference between good manners and election law. Your post seems to confuse the two. What possible legal basis is there for ruling that Trump is ineligible — because he has said harsh things about other candidates?
There is no legal basis for excluding Cruz.
Trump is not a republican.
RNC could rule he is scamming the nomination
That is reasonable
Trump hates conservatives
Why should RNC allow him as a nominee. If Bernie said he was a republican should we accept that ?