Because of political expediency

That's why Ms. Broaddrick.  So David Hogg, that poster child of postmodern leftism, fired off a tweet at the NRA.  Why?  Because the NRA said the AR15 is the modern day musket.  Meaning that in a world where armored vehicles, jet propulsion, computer technology, and rapid fire killing weapons exist, an AR15 is similar in needful comparison to the muskets wielded by the Minutemen against the most advanced and superior armed force of the late 18th Century.  Anyone with more than two brain cells and a semester in American history before c. 1990 would know that.

Master Hogg, apparently, has no clue.  So he immediately compares a musket and an AR15, notices the differences, eschews context (which is always important in an  age of  sanctified Presentism), and mocks the NRA with a word from his typical chest full of expletives.

In response, rather than school young Hogg on the differences between 18th Century and 21st
Century warfare, Ms. Broaddrick asks a fair question: where was David Hogg (or any gun hating gun control advocate) when AR15s were being handed out at Seattle's communist street fair a couple weeks ago?  I'll be honest, I don't recall anyone talking about it outside of Social Media.  The national press didn't highlight it.  I can't recall good, white Catholic liberals who often jump on gun cults at the first sight of an AR15 bringing it up.  I certainly don't recall any Parkland Protesters raising Cain.  Even Snopes, no friend of conservative narratives, concedes the guns were handed out.

When guns are bad: Other tweets suggest there would have been more understanding if they desecrated the statues

Perhaps I just missed it and there was outrage commensurate to that which happens any time a public display of AR15s occurs.  But I'll be darned if I can think of any.  My guess is, just like human life, human suffering, minorities and the poor, the AR15 as evil killing machine matters as soon as its usefulness to the Left ends.