How do you deal with "Crowd Engineers"?

I guess you only get these in smaller shows but I'm sure they're everywhere.

You know the ones that come up to you and say "it needs more bass!!" After you've just spent 5 mins trying to tame the low end that was burying the mix.

I've had one guy try to tell me I needed more "3-5k" in the guitars - tbh I admired that he knew as id cut around 4k on the whole foh as it was just horrendous on the PA and i actually care about both mine and the audiences ears.