My uninformed opinion is that cancelling primaries is not a good thing, BUT the primaries in California are part of a larger statewide, state-paid, election. That said, the decisions to cancel were made by the parties of the several states, not by the national R party, and not by President Trump.
All in all, I really do not see how Walsh thinks calling the Republican Party a "cult" is going to win him Republican votes, even from fellow Never-Trumpers. Walsh's goal, as best I understand it, is to siphon off enough votes from Trump so that the Dem - whoever he or she is - will win. Because I do not think Walsh so deluded as to think he has any chance of becoming President. With that being his goal, insulting the people whose votes he wants to divert seems to be a self-defeating move.