Black Farmers and Socially Disadvantaged Farmers Increased Market Share Act This bill addresses ways to increase market access for socially disadvantaged farmers and ranchers and to ensure civil rights accountability for Department of Agriculture (USDA) employees. ( Socially disadvantaged farmers and ranchers are those who have been subjected to racial or ethnic prejudice because of their identity as members of a group without regard to individual qualities.) Specifically, USDA must establish a program to make grants to support new or expanding food hubs designed to increase market access for socially disadvantaged farmers and ranchers. USDA shall establish a process to prioritize the purchase of agricultural food products from socially disadvantaged farmers and ranchers. That process must account for barriers to market entry faced by socially disadvantaged farmers and ranchers while maintaining the integrity of the purchasing process. The bill also establishes an agriculture hub income tax credit, which shall be an amount equal to 25% of the qualified food hub expenses for the taxable year. USDA must (1) ensure that its officials and employees are held accountable for engaging in discriminatory or retaliatory actions, harassment, civil rights violations, or related misconduct; and (2) bear the burden of proving by substantial evidence that an adverse decision was valid.