This is the autozone set I was talking about. $7 for 5 taps and a handle.
AutoZone.com | ThreadRepair | 6pcs.SAEtapwrenchset
If your M6 bots stripped out, the hole does not have enough metal to allow for threads. The threads have pulled out. Options at this point are to 1) fill it and drill and retap to M6 or 2) tap to a larger size such as 1/4 20. Option 2 is much easier.
Don't try using pliers. It can technically be used but is more difficult. The tap t handle will allow you keep even pressure and keep it straight. Splurge for the tap handle and you will be much happier than the alternative.