Big Tech Fights Back by Casting Itself as Small Firms’ Protector

Online platforms made Mimi Striplin’s dream of selling handmade jewelry possible. Initially selling her earrings and purses on Etsy Inc., Striplin built enough of a customer base to quit her day job, market her wares on Facebook and eventually open a shop on Spring Street in Charleston, South Carolina, where new customers and devoted fans find her on Google Maps.

Earlier this year she spoke with the offices of her South Carolina senators to warn that antitrust bills introduced in Congress risked complicating the online tools she uses not just to reach customers, but also to organize her team, ...