This is fine, but I do think it's a little cavalier about exactly what trade-offs libertarians (and really anyone who isn't completely happy with a candidate... which is everyone I think) face.
Assume candidates R, D, and L, and voters A, B, C, D, E, F, and G that have the following ranks for the candidates:
A: R (1) D (2) L (3)
B: R (1) D (2) L (3)
C: R (1) D (2) L (3)
D: R (2) D (1) L (3)
E: R (2) D (1) L (3)
F: R (2) D (1) L (3)
G: R (?) D (?) L (1)
G likes to think of himself as a supporter of L, and not as a pseudo-R (or for that matter, a pseudo-D). And that's an entirely coherent position to take. I've left question marks for the rankings of R and D by person G because supporters of L may very well be split on that sort of assessment. But just because G is decidedly an L, that doesn't mean his rankings of R and D are irrelevant to his vote.
L will not win. But I like the capacity for human hope, so let's say that that's one reason to vote for L.
Another reason for G to vote for L is that achieving G's goals is best served by making L and her ideas more prominent. Or perhaps voting for L this year makes L's victory four years from now more likely. Or perhaps voting for L will make both R and D act more like L in the future. All of these are good reasons to vote for L, and everyone is going to put their own weight on each of those reasons.
But the ranking of R and D is still not irrelevant, even if you like both of them much worse than you like L.
If you think you'll never live in the America you'd like to live in you'd at least like it to be closer to the America you'd like to live in. The probability of that happening may be much higher with R in office than with D in office. It's not your first choice, but if you discount your first choice by its probability of success, voting for R may be a very good move. Maybe voting for R will make D act more like R, which is not as good as getting D to act like L, but is still better than having D win and act like D!
A broader point.
Part of me finds libertarian complaining about Ds and Rs extremely obnoxious. You guys at least have a guy that agrees with you on all kinds of points that you can vote for. Plus it's chic to be a libertarian right now - it's not hard at all. Try arguing that we oughta invest more in drones. THAT'S a tough position to maintain these days.
Same with Keynesianism outside select circles. You at least have Gary Johnson. None of the candidates conforms to my view of ideal economic policy the way Gary Johnson conforms to most of yours. Living with the second best is just part of every day life for me because I don't even have a first best option to choose from. Even the prominent politicians and former politicians I'm positively disposed to - Bill Clinton, Barack Obama, Mark Warner - have major blindspots on all sorts of issues, including economic issues (which are important to me professionally but also critical for national life at this point in history).
So my participation in democratic life is entirely about second-best options and really always has been. What's more, I think this is where most Americans are at. I don't think there are a lot of people that are always highly satisfied with a candidate. Perhaps it's precisely because libertarians have a party which (while it may not be perfect) is actually structured deliberately around their well defined ideology that they sometimes bristle at the very idea of thinking about why they might vote for second best options.