I actually support letting most Dreamers stay, but there are some pretty poor, disingenuous arguments being advanced in support of that.
The Cato Institute article is...not good. As has been pointed out, and should be obvious to anyone approaching this from a neutral perspective, H-1B visa holders are a terrible proxy for Dreamers. It's such a shoddy bit of analysis that I wouldn't trust a single other thing in an article that did that.
Just for starters, you only get an H-1B if you already have a guaranteed job in a "specialty occupation" requiring "highly specialized" knowledge. These are by definition people who already have proven themselves professionally successful, gainfully employed, and have (almost universally) obtained at least a bachelor's degree in a useful field.
Dreamers include current high school students, people who only got a GED, and/or never attended (much less graduated from) college, as well as college students with crappy degrees who can't find good jobs. While some percentage of Dreamers will find success equivalent to what all H-1B visa holders have already achieved, a great many certainly will not. Cato surely knows that, but used it anyway. That's really quite despicable.