You're only marginally not a cheater.

You were sent an invite to this "group" because you fled the scene of an invasion in Dark Souls with a heroic ALT+F4.

The only worse sort of player than you is a hacker. It's debatable whether or not you're cheating, since you're exploiting out of game mechanics to circumvent the punishment for an ingame one.

The invasions are a part of being human in the game. There have to be consequences to being able to summon help.

If you can't accept the nature of how Dark Souls works, then play in offline mode or just quit the game altogether. You don't have what it takes - let's not kid ourselves.