DC is not a state. The city council owes its charter to and exercises power with the blessing of Congress thus DC is entirely bound by the US Constitution; it is not afforded any protections or exceptions that autonomous state governments are.
Heller v DC struck down DC's handgun ban in 2008; this recent case (that your link discusses) was challenging DC's standards for issuing carry permits.
DC lost at the district level in 2014, lost again at the circuit level and earlier this month (Oct) has chosen not to challenge the ruling to SCOTUS (as it did with
Heller, much to the consternation of the left). DC has been served with the court's mandate and now must issue a carry permit to any law-abiding citizen of the USA.
As for state laws being struck by the Supreme Court as federally unconstitutional, the Supreme Court struck down Chicago's handgun ban in 2010, two years after
Heller. That case was
McDonald v Chicago. and the Court enforced the 2nd by incorporating it under the 14th Amendment.
McDonald was the very
first time that a state / local gun law was invalidated as a violation of the right secured by the 2nd Amendment. Again, for like the 5th time, until 2010 the 2nd Amendment had zero effect or impact on state or local law.
The effect of
McDonald has been stalled for the time being; there are a few cases challenging state assault weapon bans in the pipeline, it might be a year or more before the Court accepts one of those cases.
Your equivalency is still incorrect; the reason why a 2017 state law on bump stocks might pass federal constitutional muster has nothing to do with why the 1830's Univ. of Virginia gun prohibition did not violate the federal right to keep and bear arms.
But you are not making a legal argument, you are making an emotional one that is divorced from any legal reasoning or legal precedent. That's fine to do, but stop couching your theory in constitutional law.
.