Would the antilock brake light come on if your rotors are bad?

no, its electrical fault i know it can make the anti lock come on if metal shavings are magnetically attracted to the anti lock sensor it will mess up the sensors reading and signal to the abs computer. so yes a grind-ed down rotor can affect abs not a warped rotor though also if the trigger wheel is attached on rotor and has a crack is will put on abs light gspeedshop