"who dare voice an opinion where HRC is not the best all and end all"
No, Clinton will receive votes from many people who would much rather vote for somebody else.
However, given a choice between Clinton and Trump, she becomes the only choice.
It comes down to Obama's comments after Trump couldn't resist tweeting abusive comments about the family of a Gold Star soldier. (Note - not a disagreement about policy, but disgust at a man who can't resist social media trolling even when he is standing for president).
there have been Republican Presidents with whom I disagreed with, but I didn’t have a doubt that they could function as President. I think I was right, and Mitt Romney and John McCain were wrong on certain policy issues, but I never thought that they couldn’t do the job. And had they won, I would have been disappointed, but I would have said to all Americans they are -- this is our President, and I know they’re going to abide by certain norms and rules and common sense, will observe basic decency, will have enough knowledge about economic policy and foreign policy and our constitutional traditions and rule of law that our government will work, and then we’ll compete four years from now to try to win an election.
But that’s not the situation here.
The US needs a president who is ideally competent, but if even that isn't possible, somebody who will listen to advice and act like a president. The Republicans are dropping support for Trump because they know that even if they can control Senate and Congress, they can't control a man who can't control himself.
Whatever the rights and wrongs of Clinton, we have somehow reached a point where she is the only viable person standing. At the moment the Republican party don't have a candidate.