I'm a massdrop member, and have been satisfied with their process, but I've read plenty of examples in which mistakes were made. And since they're a small company with narrow margins they can only stand behind "their" product to a limited amount, which has made a number of people angry when (someone else's) mistakes were made and it impacted that particular buyer. "Group buys" aren't for everyone – it's a realm filled with risk, the principle of which is even getting your product in the first place.
Also, considering keyboards and yarn are some of their better sellers, I'm betting most of their existing userbase is pretty far into the left. Selling firearm related things could chase off so much of their virtue signalling userbase they'd never recover – and the FUD surrounding the possibility would prevent them from trying, I think.
Although considering some of their other, recurring items are thousand dollar headphones, and multi-hundred dollar fountain pens, most of their targeted clientele are the unduly rich. And guns have often been a point of pride to distinguish the haves, from the have-nots; it's why Negotiate Rights Away gets so much money; they make the rich feel more secure, knowing only other rich people have guns. So, this might work.
Have you created a poll, OP? That's how you convince them to branch out, not by posting to potential customers to a group-buy that hasn't been contemplated yet.