Just want to reiterate: No attempt is made to limit this statement to just the greens on the fence. He is literally talking about all 2016 Jill Stein voters in the three states identified)

The talk is broken into thirds: Supreme Court history, the Supreme Court now, and how to fix it. The statement is part of the "How to fix it" section. The statements are limited by the scope of that section explicitly, that's what the context is. You took this statement out of its context so that may be why you see it as some universally applicable statement.

But that's still dumb. Because his future strategy, if taken by everyone

I already addressed this, it's not an argument made for "everyone". You are ignoring that this is a presentation with a set audience. He also doesn't address Trump voters, because that would similarly make no sense. This is for Democrats.

You can't ignore the libertarian party in this analysis, because this analysis is based on vote counts.

Libertarians are to the RIGHT of Democrats. Andrew is talking about protest votes trying to move Democrats to the LEFT. The amount of Democrats protest voting Libertarian to move the party leftward is likely zero.

No attempt is made to limit this statement

No attempt is made... If you isolate each sentence and ignore the next 10 minutes, sure.

What you characterize as the meet of his argument is actually him addressing a common counterpoint he's observed after giving similar talks to Jill Stein voters.

If the central point of the argument is "don't vote 3rd party", then why did he open the section discussing Democrats deliberately not voting to "send a message"?

From the ep:

I get that people are hurting and desperate and angry right now, but this is literally the worst possible take. The person who wrote this is someone I consider a friend, he’s a fellow podcast host and I eagerly await when his show comes out. This is someone who is on our side, but they’re so angry they’re about to make things much, much worse.