Then cite some real world example from other "open primary" states, whereby the conservative candidate was prevented the nomination, by cross-over voters.
As I already stated, I investigated the claim a few short years ago, and it was not proved by real world results.
Your investigation may not have been deep enough. AZ senatorial election, 2010. McCain beat a more conservative opponent because enough Dems, posing as Indies, crossed over to vote for him. There's one firm example. Same seat, 2004, same thing, so there's another one.
AZ 2012 is a different case, because Jeff Flake
was considered to be the most conservative (his record in the House was pretty good), and since it was an open seat (therefore more competitive), the Dem/Indies voted on the Dem side. They will go to Flake next election, because Flake turned out not to be any kind of conservative in the Senate. Then again, Flake may be in trouble because his son was caught letting two dozen good dogs die of heatstroke in a kennel he operated in Gilbert.