Wow um...
I wouldn't go that far, deleting your character. It's a more "don't ask don't tell" type of thing. I can PROMISE you someone you've run with in the DF has had one going at SOME POINT in your playtime. In that way, literally all players have been "tainted".

Honestly if you didn't know one was used and no one told you, how did you get the advantage? If you went up to a random person and said, "I'm sorry but I was in an FC that used DPS meters, but they never told me my numbers and I never asked," the response you'll get is "...so what?" or "Um, okay." People only really start getting upset with them once people get kicked out of parties simply for not having enough DPS (which was tracked and measured by a meter, not by...things not dying).

So really... I think you're over thinking it a little.