I really like this that you wrote....
"For me, the purpose of the instructions in Scripture on the observation of another's fruit, is not so I can then go and attempt to instruct them of what their fruit "should" be, but it's to make me aware of what fruit they are feeding me. If they are trying to instruct me without any fruit of life in their own walk, then that would indicate I should be very cautious in receiving anything from them. "
Yes, I see what you are saying and I believe that is wisdom.
What do you think of this that Jude speaks of....
"Jud 1:20 But, ye, beloved! building yourselves up in your most holy faith, in Holy Spirit, praying,
Jud 1:21 Yourselves, in God's love, keep,—awaiting the mercy of our Lord Jesus Christ, unto age-abiding life.
Jud 1:22 And, on some, indeed, have mercy,—such as are in doubt, be saving, out of the fire, snatching them;
Jud 1:23 But, on others, have mercy with fear, hating even, the garment, spotted by the flesh.
Jud 1:24 Now, unto him who is able—to guard you from stumbling, and to set you in the presence of his glory, without blemish, with exultation,—
Jud 1:25 Unto God alone our Saviour, through Jesus Christ our Lord, be glory, greatness, dominion, and authority, before all the by-gone age, and now, and unto all the coming ages. Amen!"
I see these scriptures as being what our role IN CHRIST is to be for all those that are 'spotted by the flesh'.....
It seems that you are stating what Jude 1:23 is stating....that we are to recoginize other's fruit or lack thereof so that we will not be polluted with what comes out of their own mouths/hearts....for out of the overflow of the heart doth the mouth speak.
Ultimately....it is as Jude says....UNTO GOD ALONE....UNTO HIM WHO IS ABLE ....to guard you from stumbling....wheww....HalleluYah!