There's nothing unconstitutional about "private clubs". If you don't like their rules, start your own. If you want to join theirs, you play by their rules.
There is no reasoning with the unreasonable here. I’m not even going to waste my time trying, but good luck to you. They (Trump followers) don’t understand and they probably don’t want to understand.
http://www.washingtontimes.com/news/2016/apr/16/reince-priebus-blasted-major-breach-trust-top-rnc-/
Read it and weep: current RNC rules allow Priebus to parachute in a new nominee even if the rules committee has disallowed it and a majority delegates have voted against it. Still love the party rules?