For one, if something is described as "carbrained," the subject is discounting, ignoring or outright rejecting alternatives to driving. A carbrained take would not necessarily be one that prefers cars. A carbrained take would include things like:

"the only way to make more room for people to move from A to B is by adding more lanes to highways!" (a concept that's proven to only make traffic worse)
"This cycling lane is not being used. Let's remove it!" (Which may be a fallacy based on the fact that cyclists move more freely in seemingly confined space, or the fact that the specific cycling lane in question may be an isolated lane with no origins and destinations on it)
"What? A bus lane? What a waste of space! Let me drive there!" (where the speaker fails to see that one bus easily holds four dozen people, which would mean four dozen cars not on the road, if & only if that bus is not affected by road traffic.
"We're wasting money on this high speed railway line between these two cities about 500 km apart!" (failing to see that distances between about 300 to about 800 km are the sweet spot where high speed rail is exactly in that sweet spot of distance where it's faster than both driving and flying.)

For two, the car lobby is already great at needlessly extending commutes. When the Katy Freeway near Houston was expanded to its current width of 26 lanes, the widest in the world, travel times changed from end to end from just around three quarters of an hour, to more than a whole hour. An increase of about a third. I could go on and on about this, but let's just say that it takes a lot more to make trains work worse, and generally, if you try to ameliorate transit service by expanding it, that makes transit better for everyone, including car drivers, unlike if you expand highways.

The thing of the anti car dependency movement is that they demand more developments to not to have to drive. They demand more space be dedicated to more sustainable developments, with less parking, uses closer together, more room for people out on foot or bikes to get where they want to go, all that jazz.

Ultimately, the anti car dependency movement wants freedom. The freedom not to have to drive if you don't want to, don't need to, or for any reason cannot. And that is what carbrained people are not getting.