With all due respect, Reagan’s so called Eleventh Commandment was more of a quip than a core principle. He was more than willing to criticize Jerry Ford in 1976...although he did fall in line and support the eventual nominee.
Which is the whole point. Fight it out in the Primary (like Reagan did) and then fall in line against the enemy if you don't win (like Reagan did in 76 and 72 and 68 and 64) and if you do win the primary, then respect and expect the support of those who didn't win likewise (like Reagan did in 1980)
What we've got now is a bunch of people who either get their way in the Republican primary, or else they work for helping elect the Marxist to destroy the country. Insane.