Notice the term "commonsense" (sic) is used. Coupled along with the slickly coined term "mass casualty weapon" the author of the bill is trying to craft it in such a way to make it appear unacceptable to oppose it.
The bill allegedly exempts firearms chambered in .22 rimfire variations, but this exception is illogical to their reasoning. A .22 certainly can prove fatal to a human being, and I recall reading that the .22LR has caused a disproportionate number of fatalities compared to other chamberings.
Legislation like this is the gateway to impose more draconian restrictions. If this were to become law, it could easily lead to more "common sense" restrictions on guns. Why would they feel obligated to stop at semi automatic firearms? A lever gun or revolver can put a significant volume of fire downrange quickly. What is the definition of "mass casualty"? More than a single victim?
Like the litigation in Chicago mentioned demonstrates, it is obvious that criminals don't obey the law. Short of confiscation, what will they do about those firearms already in the hands of legally qualified gun owners? Quite likely, confiscation will be argued to be necessary to enforce the prohibitions.
When someone who opposes this bill speaks out against the potential for tyrannical abuse inherent in this bill, they will almost certainly be labeled as a fear monger or a conspiracy theorist. As per the standard playbook of the left, they want to have the luxury of accusing their opponents of using the same tactics they are engaged in. Just because you call the other guy a liar first, that doesn't make you truthful. Sadly, there's a lot of unthinking people who follow that logic and will blindly accept that reasoning.