NEW YORK (AP) — A racist ideology seeping from the internet’s fringes into the mainstream is being investigated as a motivating factor in the supermarket shooting that killed 10 people in Buffalo, New York. Most of the victims were Black. Ideas from the “great replacement theory” filled a racist screed supposedly posted online by the white 18-year-old accused of targeting Black people in Saturday’s rampage. Authorities were still working to confirm its authenticity. Certainly, there was no mistaking the racist intent of the shooter. What is the ‘Great Replacement Theory’? Simply put, the conspiracy theory says there’s a plot to...