At least some former FBI agents would rather defend their country than terrorize their fellow citizens. In a letter dated Jan. 17 — addressed to congressional leaders and relevant committee chairs — a group of 10 retired federal law enforcement officials warned that President Joe Biden’s dereliction of duty at the nation’s southern border placed Americans at severe risk of unprecedented attacks on their homeland. Republican Sen. Ron Johnson of Wisconsin posted the letter Thursday on the social media platform X. “This sobering letter from former FBI, Homeland Security, and other law enforceme…