The AVERAGE size of a vehicle is literally irrelevant to the discussion. You asked what people with 3-4 kids did 20 years ago: My response was they bought the same Tahoe they buy now. Which was nearly identical in size. You keep saying "The average size" when it has little to no bearing on OPs complaint: which is he wants to eliminate full-size SUVs and trucks.
YOU implied that full size SUVs and trucks weren't a thing 20 years ago by asking what people did. Now you're moving the goal posts because I pointed out how silly your implication was. The Tahoe having its wheelbase grow 4" in 20 years isn't what OP is complaining about and you know it.
Let's quote what GP said: "There is zero reason a person needs to own a 7 seat SUV to transport 3 people or five 2x4s twice a year. The proliferation of oversized vehicles continues to exacerbate a significant number of local and global issues and I'm of the belief that we need strong regulation to limit the size of vehicles.". You chose to interpret "proliferation of oversized vehicles" and "strong regulation to limit the size of vehicles" as "eliminate full-size SUVs and trucks". I have no idea how you got there and what your definition of "large" here and how it follows from what GP said. That's what I mean by you creating a strawman. If you steelman the argument, you wouldn't get "eliminate full-size SUVs and trucks" from it.