No, you don't need a pickup to tow a tiny aluminum boat to go fishing. I'm well aware that there are many people driving huge trucks/SUVs around who don't need them. That's quite different, however, than saying no one has a legitimate use.* Bigger boats (around here we have ocean going vessels), gooseneck trailers, or heavy loads. If you're moving more than 5000 lbs you're more or less limited to a pickup/SUV.
That said, I'm all for policy to nudge people in a better direction. IMO the CDL route is too heavy handed, think a tax is more appropriate. But whatever, difference of opinion.
If the goal is reducing GHG (rather than lashing out at symbols of the culture war) then the number one thing we can and should do in the US is build denser cities - especially along the West Coast. What good does it do to drive around in a Tesla while insisting on suburban level density? This leads to urban sprawl and super commutes for many thousands of the less well off. Oh, right, we can feel smug in our elitism while enjoying our exclusive leafy neighborhoods. Dense cities result in less driving for everyone, and they also encourage smaller vehicles. Yet here I sit, in one of the supposedly "greenest" cities in the US, advocating for higher density while most of my neighbors fight to stop all development. It's messed up.
*About legitimate use: Does anyone need horses, or a big boat, or any other hobby requiring a big vehicle? Strictly speaking, no. But by definition no one "needs" any particular hobby or leisure activity. So if that's going to be the criteria for what we allow in society then we should ban all air travel for non-work reasons. In fact, all travel to any destination for non-work reasons should be disallowed. Entire industries should be shuttered...surfing, biking, skiing. These all have an enormous footprint. Obviously I don't really think we should do this, but pointing out that we should be careful about picking on certain groups of people just because we don't like them.