There is no “right to vote” in the Constitution. The determination of who is eligible to vote is a power reserved to the states. There are amendments related to infringing that right.
The processes by with the parties select delegates have been available to all. One candidate paid attention. One did not.
Let the process play out.
It is extremely difficult to execute a "choice" to participate by voting or not when there isn't a "vote" by the entire Republican electorate offered in the first place. Colorado, to be exact. There were 'opportunities' for the vigilant citizen voter to 'participate' in a series of multiple meetings in cabal-ish venues controlled by party bureaucrats (4-5 as I recall), but NOT ONE OPEN ELECTORATE-ADVERTISED VENUE WHERE ALL REPUBLICAN VOTERS could voice their chose on ONE DAY, ONE VOTE. This isn't voters choosing not to participate and you know it.
In Colorado, only a few thousand out of 3 million Republicans participated in the caucuses, which ultimately had almost no impact anyway in terms of reflecting even the will of the few thousand that managed to come home from work, take care of their families, hire babysitters, and then waste two hours going to nearly meaninglessly “caucuses”, because the few thousand were eventually randomly reduced to a few hundred who attended Congressional or State assemblies to vote on national primary convention delegates.
This is a particularly onerous process for a state that otherwise conducts mail-in ballots by all registered voters for all other elections.
Nonetheless, I assert that if the above Colorado caucus process is such a great way to nominate a GOP candidate, then Colorado should duplicate this exact process for ALL of its elections.