If 200k people would show up, yeah, it'd make a difference. 200k people not yelling chants, or waving scary guns around. The person who felt the need to resort to saying I'm the one on my knees, or interested in male parts, would be the one that the cameras would focus on and you'd still lose and lose big.
Until the 2A supporters quit eating their own, we'll never win. It's not about boycotting, we simply are not a large enough group to pull that off. The stats don't lie, most guns in the United States are owned by a small group of people. The 300 million firearms aren't owned by 300 million people (obviously), cut out the fuds and the number gets even smaller as to people who really support the 2A.
By comparison, the state overall has about 413,980 active permits as of Jan. 3, a licensing rate of 61 permits for every 1,000 residents, Mass news article taken from a 2017 article, you'd need 50% of every permit holder in the state to get to your 200k number, how likely is that? That number dropped to less than 400k in 2018. How many of those 400k permits are fuds who think they'll never come for their shotgun or bolt rifle? Simply put, the masses of Mass either don't care or are anti-firearm. You have a shot at the 'don't care' crowd, the blindly anti-2A are pretty much a writeoff.
Link to article:
Concealed gun permits on rise in Massachusetts