To be clear they were not accused to of being anti-social. People who don't want gun manufacturers sued for what is done with their guns were called child killers, "sandy hook hoaxers", etc. The Bloomberg (yes, it was Bloomberg) money machine paired with the noise machine that is Mom's Demand Action has absolutely dominated the narrative around this.
But I think the real reason gun manufacturers are getting targeted is because the people who have been victims of gun violence see no other recourse. Gun control in the US is mostly laughable, and it's politically difficult (if not impossible) to fix these sorts of problems. So the next natural step is to probe the system to see if there are any creative ways to change things. Targeting gun manufacturers with lawsuits is one of those possibilities.