Since I have been considering penning something similar today (and for the past few weeks), I will eschew that and add this:
If you truly don't believe Hillary Clinton or Donald Trump are fit for the office of the Presidency, then any attack from the Trump camp about "getting Hillary elected" doesn't matter. The Trump camp is simply asking us to trade one unfit candidate for another, possibly more dangerous, one, solely because 1) he's a Republican, and 2) he says things even though they run counter to what he's said and done before and counter to what we believe. Besides, so what? If Hillary Clinton does get elected because we refused to be browbeat into submission, we've already lived through eight years of Obama, and Hillary LOST to him. Hillary's weaker, more damaged, and has far less of a mandate. If she's anything like her husband, with a Republican Congress she can be kept in check. With Trump as titular head of the GOP, a Republican House will do his bidding quickly.
As Abaraxas said, Johnson has a record of governance in his two terms as governor of New Mexico (which, unlike a certain Trump-supporting fallen superstar, he did not quit). It was OK—maybe not a conservative's dream, but it was respectable. If that is the record on which we're going, a Johnson Presidency will at least buy us time. If the election comes down to Trump, Clinton or Johnson, I think most of us could live with Johnson better than Trump or Clinton.
The likelihood that Johnson will win, of course, is quite narrow. His best hope is in picking off electoral votes. His high point was in New Mexico, where last month he was polling upward of 25%, not far behind Evan McMullin's Utah polling, which showed him at 30%. However, it's my firm belief that eventually we are going to need to move on, and that the Republican Party is dying a slow, Federalist-style death. To prepare for that, we need to have a replacement ready. With the younger generation's rejection of social morality, the Libertarians, who to their credit have built the political framework needed to be able to compete in a national election, would make natural allies for the conservative movement, just as many of them were during the Tea Party movement. They would need to be kept honest, and remember that there is a time and a place for pragmatism, things that past leaders in the party haven't embraced. Even if Johnson isn't within striking distance in most states, there are other benefits a party can gain from a strong poll showing.
My one caveat is in Utah, where I would recommend voting McMullin, simply because we need to pool as many third-party votes together as we can. Unchecked, the two-party system is on its way to a one-party system if we don't change course.