"if you are a sinner yourself, you cannot speak against sin and condemn it"
But, I have a problem with this. I think there is a principal called 'objectivism' meaning that when sth is correct, it is correct. No matter how we think and act. And when sth is wrong, it is wrong. No matter how much sinful and dirty we might be.
Therefore, if I am a theif, I can say "theft is wrong" and you must agree with me, since I have declared an objective truth. You should not think about my being good or bad, just the truth of this statement.
It is why I think that the first sentence is against objectism.
the other problem: If I am guilty of X and an ignorant comes to me and asks whether X is good or bad, shouldn't I tell him that X is bad?
If I am a sinner and some body wants to imitate my sins, shouldn't I tell him not to do so?