That seems like a strawman. I for one do not think a trump presidency was a worthwhile trade for sending a vague signal to the democrats that they should "course correct".
How diverse is the set of people you speak to? In the last 4 years, I've heard the following sentiment often: "I don't like the guy and his rhetoric, but at least Trump has caused fewer deaths in international conflicts than Obama did" (and with a belief that Hilary would have been worse on this metric). I do not know how true this claim is, and it's hard to get concrete numbers, but a concern over foreign policy is usually much greater amongst 3rd party voters than for Democrats and Republicans.
Don't assume everyone who didn't vote for Hilary shares your perspective, and rhetoric like yours continues to alienate independent voters.
>In the last 4 years, I've heard the following sentiment often: "I don't like the guy and his rhetoric, but at least Trump has caused fewer deaths in international conflicts than Obama did"
That sentiment doesn't really say anything about whether it was a worthwhile trade or not. Kind of like a restaurant review that says "the food was shit and the service times were slow, but at least the waiters were nice" doesn't really mean that the restaurant is good overall, or whether they would choose the restaurant next time over a competitor.
Voting for a third party tells the parties that if they don’t course correct at least a little they risk losing elections to the other guys.
That’s only a problem for the individual voter if he holds the view that this election is the last election. “We have to beat the other guy or the world is going to end.”
Contrary to the marketing, you’re not helping the other side win if you vote third party. The candidates/parties are doing that by not offering you a decent candidate.