As long as you leave within a reasonable time frame upon realizing/suspecting a fireteam member is cheating you should have zero fear of being hit by ban shrapnel. As for reporting the cheater, you can file a report after the fact through the following link: https://help.bungie.net/hc/en-us/articles/360049497451-Report-Suspected-Cheating Be sure to fully read the instructions listed before filing a report to ensure your situation fits the given parameters and you supply the necessary information. (΄◉◞౪◟◉｀)