I look at it like this, why should people get a choice to keep stats they haven't earned at the expence of those that have lost stats that they have earned.
A stat system needs to be fair (more so if it actully affects things ingame like this games stats do) and resetting all stats (when it gets fixed) is the only fair thing to do. Giving people a choice isn't a valid or fair option because people who perhaps have had a massive stat increase they didn't earn can choose to keep that increase.
On top of this, unless evey player has kept a count of all their kills themselfs there is no way to tell if their stats are bugged or not. As such, people who say "i want to keep my stats, they're working fine for me", ask yourself this, how exactly do i know the stats are working fine for me?., you simply don't.