That's a good point (no irony intended)

The actual actions of Biden and his place in the Moral scale aren't really speculation (supporting with military hardware and ammo a Genocidal fascist ethnostate because of the dominant ethnicity of that state - check!), but the part about the DNC does indeed fall into the realm of speculation.

Further, from his historical track record it seems likely that Trump wants to take over power and become some kind of dictator - he says a lot of things and then doesn't go forward with them, but this one he said it and tried it - however, what's in doubt (IMHO) is whether he actual can do it.

On the side of the DNC, from decades of historical track record it seems very likely that they do not want a more leftwing Democratic candidate and from recent history and the whole Democratic Primary structure, most noteably the anti-Democratic super-voters, it's clear that they also can stop a more leftwing candidate, as that's exactly what they did with Sanders.

So it's a don't vote Biden and if Trump wins he will try to become a life dictator but might or not succeed or vote Biden and if he wins the Democrat Party will keep on shifting right (and there's not that much right to shift to, since this election is "quasi-Nazi"-supporting hard neoliberal - vs - Fascist) and eventually the Democrats will be fielding a Trump-like candidate and the Republicans a Worse-than-Trump one, with a very low probability of it not being so (it would require a change of a trend of 3 decades without anything at all forcing them to do so, hence probabilitically a Fascist -vs- Fascist election in the US it's mainly a question of when rather than if).

It's a Trump-today vs Trump-like-or-worse-tomorrow scenario unless (if they vote Biden now) people find a way to shift the direction of things in the time between, and I have yet to hear a single realistic way to do that for the Presidential elections, though I've seen a few good ideas to push the Democrats left in Congressional and Senate elections, through civil society movements and targetted campaigns in the Primaries against the most rightwing Democratic candidates.

As I said, it's a fucked up "choice".

PS: For me the best result (IMHO) might be a barely by the skin of their teeth Democrat victory - just about enough to stop Trump and so close to a Democrat loss that it makes the DNC fear that they've shifted too much to the Right - however such an outcome is impossible to organise and even if it does happen, my hope of how the DNC gets affected is still all speculation and might be totally wrong.

When talking about Biden, they're talking about the consequences to democrat party structure. When talking about Trump, they're talking about policy. Their point stands